L-Phenylalanine

availability_state

biomarker_context Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Human PET loading study in six men.

limitations

ACHC is a transport tracer; each individual natural amino acid was not directly measured. This is not a normal-meal threshold.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A large phenylalanine load can compete with other molecules for brain entry.

primary_references

Inhibition of neutral amino acid transport across the human blood-brain barrier by phenylalanine. · 1995 · https://pubmed.ncbi.nlm.nih.gov/7861158/ · DOI 10.1046/j.1471-4159.1995.64031252.x

trigger_kind

biomarker_context Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 190–196

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human PET loading study in six men. · source_derived_draft · unverified_draft

## l-phenylalanine-brain-competition A large phenylalanine load can compete with other molecules for brain entry. After 100 mg/kg oral phenylalanine in six healthy men, plasma phenylalanine rose about elevenfold and brain uptake of the artificial large-neutral-amino-acid tracer carbon-11 ACHC fell from 0.036 to 0.019 mL/g/min. Model: Human PET loading study in six men. Limitations: ACHC is a transport tracer; each individual natural amino acid was not directly measured. This is not a normal-meal threshold. Evidence access: Primary abstract Inhibition of neutral amino acid transport across the human blood-brain barrier by phenylalanine. · 1995 · https://pubmed.ncbi.nlm.nih.gov/7861158/ · DOI 10.1046/j.1471-4159.1995.64031252.x

evidence_access

Primary abstract

experimental_model

Primary mouse I cells; stereoselective L- versus D-phenylalanine responses.

limitations

Cell assay responses do not establish that calcium supplements enhance satiety in humans.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Gut amino-acid sensing can depend on both the amino acid and calcium.

primary_references

The extracellular calcium-sensing receptor is required for cholecystokinin secretion in response to L-phenylalanine in acutely isolated intestinal I cells. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21252045/ · DOI 10.1152/ajpgi.00342.2010

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 278–284

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Primary mouse I cells; stereoselective L- versus D-phenylalanine responses. · source_derived_draft · unverified_draft

## l-phenylalanine-casr-cck Gut amino-acid sensing can depend on both the amino acid and calcium. L-phenylalanine stimulated CaSR-dependent calcium signaling and CCK release in primary mouse duodenal I cells; CCK responses were greater at 2.5 than at 1.26 mM extracellular calcium. Model: Primary mouse I cells; stereoselective L- versus D-phenylalanine responses. Limitations: Cell assay responses do not establish that calcium supplements enhance satiety in humans. Evidence access: Primary abstract The extracellular calcium-sensing receptor is required for cholecystokinin secretion in response to L-phenylalanine in acutely isolated intestinal I cells. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21252045/ · DOI 10.1152/ajpgi.00342.2010

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Single historical infant case with combined phenylalanine/tyrosine restriction and repletion.

limitations

Cannot attribute every manifestation to isolated phenylalanine deficiency or generalize a dose threshold.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Over-restricting these building blocks can create a new shortage problem.

primary_references

Phenylalanine-tyrosine deficiency syndrome as a complication of the management of hereditary tyrosinemia. · 1977 · https://pubmed.ncbi.nlm.nih.gov/835507/ · DOI 10.1093/ajcn/30.2.209

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

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AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Single historical infant case with combined phenylalanine/tyrosine restriction and repletion. · source_derived_draft · unverified_draft

## l-phenylalanine-combined-shortage Over-restricting these building blocks can create a new shortage problem. An infant treated for tyrosinemia type I developed growth failure, anorexia, lethargy and hypotonia with low phenylalanine and tyrosine during restriction; adding both amino acids reversed these manifestations without reversing cirrhosis. Model: Single historical infant case with combined phenylalanine/tyrosine restriction and repletion. Limitations: Cannot attribute every manifestation to isolated phenylalanine deficiency or generalize a dose threshold. Evidence access: Primary abstract Phenylalanine-tyrosine deficiency syndrome as a complication of the management of hereditary tyrosinemia. · 1977 · https://pubmed.ncbi.nlm.nih.gov/835507/ · DOI 10.1093/ajcn/30.2.209

evidence_access

Primary abstract

experimental_model

Recombinant human proteins; primary abstract.

limitations

GCH1 controls an early BH4-biosynthesis step; this is not proof that supplemental phenylalanine raises BH4 in every tissue.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

The substrate can signal for more of the cofactor-making machinery to work.

primary_references

Bacterial lipopolysaccharide down-regulates expression of GTP cyclohydrolase I feedback regulatory protein. · 2002 · https://pubmed.ncbi.nlm.nih.gov/11799107/ · DOI 10.1074/jbc.M107326200

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 38–44

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Recombinant human proteins; primary abstract. · source_derived_draft · unverified_draft

## l-phenylalanine-gch1-feedforward The substrate can signal for more of the cofactor-making machinery to work. Recombinant human GFRP enabled phenylalanine-dependent stimulation of recombinant human GCH1. Model: Recombinant human proteins; primary abstract. Limitations: GCH1 controls an early BH4-biosynthesis step; this is not proof that supplemental phenylalanine raises BH4 in every tissue. Evidence access: Primary abstract Bacterial lipopolysaccharide down-regulates expression of GTP cyclohydrolase I feedback regulatory protein. · 2002 · https://pubmed.ncbi.nlm.nih.gov/11799107/ · DOI 10.1074/jbc.M107326200

evidence_access

Primary full text

experimental_model

Human or mouse receptor expressed in HEK293 cells.

limitations

Millimolar cell-assay potency does not prove that GPR142 mediates every whole-animal phenylalanine response.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A second amino-acid receptor can respond to phenylalanine.

primary_references

GPR142 Controls Tryptophan-Induced Insulin and Incretin Hormone Secretion to Improve Glucose Metabolism. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27322810/ · DOI 10.1371/journal.pone.0157298

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 294–300

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human or mouse receptor expressed in HEK293 cells. · source_derived_draft · unverified_draft

## l-phenylalanine-gpr142-sensing A second amino-acid receptor can respond to phenylalanine. Phenylalanine activated transfected human and mouse GPR142 IP1 signaling with EC50 values around 3.5 and 2.8 mM, respectively. Model: Human or mouse receptor expressed in HEK293 cells. Limitations: Millimolar cell-assay potency does not prove that GPR142 mediates every whole-animal phenylalanine response. Evidence access: Primary full text GPR142 Controls Tryptophan-Induced Insulin and Incretin Hormone Secretion to Improve Glucose Metabolism. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27322810/ · DOI 10.1371/journal.pone.0157298

evidence_access

Primary full text

experimental_model

Randomized crossover intraduodenal infusion study.

limitations

This route and exposure differ from eating mixed protein; measured hormones do not identify the responsible receptor.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Directly delivering phenylalanine to the small intestine changed a human gut-hormone signal.

primary_references

Effects of Intraduodenal Infusions of L-phenylalanine and L-glutamine on Antropyloroduodenal Motility and Plasma Cholecystokinin in Healthy Men. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26130636/ · DOI 10.5056/jnm14143

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AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Randomized crossover intraduodenal infusion study. · source_derived_draft · unverified_draft

## l-phenylalanine-human-gut-hormone Directly delivering phenylalanine to the small intestine changed a human gut-hormone signal. In ten healthy men, intraduodenal phenylalanine at 0.15 or 0.45 kcal/min for 90 minutes increased plasma CCK. Model: Randomized crossover intraduodenal infusion study. Limitations: This route and exposure differ from eating mixed protein; measured hormones do not identify the responsible receptor. Evidence access: Primary full text Effects of Intraduodenal Infusions of L-phenylalanine and L-glutamine on Antropyloroduodenal Motility and Plasma Cholecystokinin in Healthy Men. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26130636/ · DOI 10.5056/jnm14143

evidence_access

Primary full text

experimental_model

Ten healthy men; 0.45 kcal/min intraduodenal infusion for 90 minutes.

limitations

Gastric emptying was inferred from motor effects rather than directly measured in this experiment.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

The stomach-outlet motor response was selective, not a shutdown of all gut movement.

primary_references

Effects of Intraduodenal Infusions of L-phenylalanine and L-glutamine on Antropyloroduodenal Motility and Plasma Cholecystokinin in Healthy Men. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26130636/ · DOI 10.5056/jnm14143

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 334–340

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Ten healthy men; 0.45 kcal/min intraduodenal infusion for 90 minutes. · source_derived_draft · unverified_draft

## l-phenylalanine-human-gut-motor The stomach-outlet motor response was selective, not a shutdown of all gut movement. The higher intraduodenal phenylalanine load suppressed antral and increased phasic pyloric pressures; duodenal pressures and tonic pyloric pressure were not significantly changed. Model: Ten healthy men; 0.45 kcal/min intraduodenal infusion for 90 minutes. Limitations: Gastric emptying was inferred from motor effects rather than directly measured in this experiment. Evidence access: Primary full text Effects of Intraduodenal Infusions of L-phenylalanine and L-glutamine on Antropyloroduodenal Motility and Plasma Cholecystokinin in Healthy Men. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26130636/ · DOI 10.5056/jnm14143

evidence_access

Primary abstract

experimental_model

Human indicator amino-acid oxidation/balance feeding study without dietary tyrosine.

limitations

Population and protocol differ from the older-adult excess-tyrosine study; different estimates are not treated as a scientific contradiction.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

When tyrosine is absent, phenylalanine must cover an additional metabolic demand.

primary_references

The daily phenylalanine requirement of healthy Indian adults. · 2006 · https://pubmed.ncbi.nlm.nih.gov/16762944/ · DOI 10.1093/ajcn/83.6.1331

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AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human indicator amino-acid oxidation/balance feeding study without dietary tyrosine. · source_derived_draft · unverified_draft

## l-phenylalanine-no-tyrosine-requirement When tyrosine is absent, phenylalanine must cover an additional metabolic demand. A tracer study in healthy Indian adults consuming no tyrosine estimated mean phenylalanine requirement at about 38 mg/kg/day. Model: Human indicator amino-acid oxidation/balance feeding study without dietary tyrosine. Limitations: Population and protocol differ from the older-adult excess-tyrosine study; different estimates are not treated as a scientific contradiction. Evidence access: Primary abstract The daily phenylalanine requirement of healthy Indian adults. · 2006 · https://pubmed.ncbi.nlm.nih.gov/16762944/ · DOI 10.1093/ajcn/83.6.1331

evidence_access

Primary full text

experimental_model

Isolated human PAH regulatory domain; 1.8-angstrom crystal structure and biophysical assays; crystallization used 10 mM phenylalanine.

limitations

An isolated domain at experimental concentrations does not establish an oral-dose activation threshold.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Phenylalanine helps switch on the machinery that processes it.

primary_references

Structural basis for ligand-dependent dimerization of phenylalanine hydroxylase regulatory domain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27049649/ · DOI 10.1038/srep23748

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 22–28

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Isolated human PAH regulatory domain; 1.8-angstrom crystal structure and biophysical assays; crystallization used 10 mM phenylalanine. · source_derived_draft · unverified_draft

## l-phenylalanine-pah-allostery Phenylalanine helps switch on the machinery that processes it. Phenylalanine bound at the interface of two ACT regulatory domains and stabilized the human PAH regulatory-domain dimer. Model: Isolated human PAH regulatory domain; 1.8-angstrom crystal structure and biophysical assays; crystallization used 10 mM phenylalanine. Limitations: An isolated domain at experimental concentrations does not establish an oral-dose activation threshold. Evidence access: Primary full text Structural basis for ligand-dependent dimerization of phenylalanine hydroxylase regulatory domain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27049649/ · DOI 10.1038/srep23748

evidence_access

Primary abstract

experimental_model

Mouse STC-1 cells, live-cell signaling and pharmacologic experiments.

limitations

Exposure details beyond the accessed abstract are unresolved; this is not direct human gut evidence.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A gut-cell model used a receptor-to-calcium pathway to release a hormone.

primary_references

Identification of a regulatory pathway of L-phenylalanine-induced GLP-1 secretion in the enteroendocrine L cells. · 2022 · https://pubmed.ncbi.nlm.nih.gov/34953208/ · DOI 10.1016/j.bbrc.2021.12.043

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 310–316

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Mouse STC-1 cells, live-cell signaling and pharmacologic experiments. · source_derived_draft · unverified_draft

## l-phenylalanine-stc-gpr142 A gut-cell model used a receptor-to-calcium pathway to release a hormone. In STC-1 enteroendocrine cells, phenylalanine stimulated a GPR142/Gq-linked calcium response contributing to GLP-1 release. Model: Mouse STC-1 cells, live-cell signaling and pharmacologic experiments. Limitations: Exposure details beyond the accessed abstract are unresolved; this is not direct human gut evidence. Evidence access: Primary abstract Identification of a regulatory pathway of L-phenylalanine-induced GLP-1 secretion in the enteroendocrine L cells. · 2022 · https://pubmed.ncbi.nlm.nih.gov/34953208/ · DOI 10.1016/j.bbrc.2021.12.043

evidence_access

Primary abstract

experimental_model

Mouse STC-1 cell transport, membrane-potential and secretion assays.

limitations

The accessed abstract does not identify a specific transporter isoform; B0AT1 is not assigned by inference.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Amino-acid transport can supply an electrical signal as well as a nutrient.

primary_references

Identification of a regulatory pathway of L-phenylalanine-induced GLP-1 secretion in the enteroendocrine L cells. · 2022 · https://pubmed.ncbi.nlm.nih.gov/34953208/ · DOI 10.1016/j.bbrc.2021.12.043

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 318–324

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Mouse STC-1 cell transport, membrane-potential and secretion assays. · source_derived_draft · unverified_draft

## l-phenylalanine-stc-sodium Amino-acid transport can supply an electrical signal as well as a nutrient. Sodium-dependent phenylalanine uptake contributed to depolarization and GLP-1 secretion in STC-1 cells. Model: Mouse STC-1 cell transport, membrane-potential and secretion assays. Limitations: The accessed abstract does not identify a specific transporter isoform; B0AT1 is not assigned by inference. Evidence access: Primary abstract Identification of a regulatory pathway of L-phenylalanine-induced GLP-1 secretion in the enteroendocrine L cells. · 2022 · https://pubmed.ncbi.nlm.nih.gov/34953208/ · DOI 10.1016/j.bbrc.2021.12.043

evidence_access

Primary abstract

experimental_model

Human B0AT1 structural and transport study; established physiological role described in abstract.

limitations

Transporter identity does not specify a universal saturation threshold.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

The gut and kidney transport machinery helps determine phenylalanine availability.

primary_references

Structure-guided development of a potent human B0AT1 inhibitor effective in a mouse model of phenylketonuria. · 2026 · https://pubmed.ncbi.nlm.nih.gov/42350764/ · DOI 10.1038/s42003-026-10535-y

transport_effect

raises Recorded as acting during intestinal absorption and renal reuptake, both of which are inward.

transport_pool

the enterocyte and tubule cell interior Recorded as acting during intestinal absorption and renal reuptake, both of which are inward.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 166–172

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human B0AT1 structural and transport study; established physiological role described in abstract. · source_derived_draft · unverified_draft

## l-phenylalanine-renal-transporter The gut and kidney transport machinery helps determine phenylalanine availability. B0AT1/SLC6A19 transports neutral amino acids including phenylalanine during intestinal absorption and renal reuptake. Model: Human B0AT1 structural and transport study; established physiological role described in abstract. Limitations: Transporter identity does not specify a universal saturation threshold. Evidence access: Primary abstract Structure-guided development of a potent human B0AT1 inhibitor effective in a mouse model of phenylketonuria. · 2026 · https://pubmed.ncbi.nlm.nih.gov/42350764/ · DOI 10.1038/s42003-026-10535-y

evidence_access

Primary abstract

experimental_model

Purified human enzyme substrate comparison.

limitations

This finding does not support TAT as an effective substitute for deficient PAH.

nutrient_topic

L-Tyrosine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Tyrosine

plain_language

Closely related amino acids are not interchangeable substrates.

primary_references

The narrow substrate specificity of human tyrosine aminotransferase--the enzyme deficient in tyrosinemia type II. · 2006 · https://pubmed.ncbi.nlm.nih.gov/16640556/ · DOI 10.1111/j.1742-4658.2006.05202.x

L-Tyrosine: catecholamines, thyroid chemistry, pigment, metabolism and cross-nutrient mechanisms (2026-09-19) · lines 220–226

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Purified human enzyme substrate comparison. · source_derived_draft · unverified_draft

## l-tyrosine-tat-discrimination Closely related amino acids are not interchangeable substrates. Human TAT catalytic efficiency for tyrosine was about four orders of magnitude greater than for phenylalanine. Model: Purified human enzyme substrate comparison. Limitations: This finding does not support TAT as an effective substitute for deficient PAH. Evidence access: Primary abstract The narrow substrate specificity of human tyrosine aminotransferase--the enzyme deficient in tyrosinemia type II. · 2006 · https://pubmed.ncbi.nlm.nih.gov/16640556/ · DOI 10.1111/j.1742-4658.2006.05202.x

evidence_access

Primary abstract

experimental_model

Human transporter in Xenopus oocytes; tracer influx and efflux.

limitations

Does not show that ordinary mixed meals deplete methionine.

nutrient_topic

L-Methionine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Methionine

plain_language

Transport depends on substrates on both sides of the membrane.

primary_references

Transport of a neurotoxicant by molecular mimicry: the methylmercury-L-cysteine complex is a substrate for human L-type large neutral amino acid transporter (LAT) 1 and LAT2. · 2002 · https://pubmed.ncbi.nlm.nih.gov/12117417/ · DOI 10.1042/BJ20020841

L-Methionine: transport, methylation, sulfur metabolism and cross-nutrient mechanisms (2026-09-19) · lines 28–34

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human transporter in Xenopus oocytes; tracer influx and efflux. · source_derived_draft · unverified_draft

## methionine-lat2-exchange Transport depends on substrates on both sides of the membrane. Human LAT2/SLC3A2 transported methionine; leucine and phenylalanine stimulated methionine efflux even against an inward methionine gradient. Model: Human transporter in Xenopus oocytes; tracer influx and efflux. Limitations: Does not show that ordinary mixed meals deplete methionine. Evidence access: Primary abstract Transport of a neurotoxicant by molecular mimicry: the methylmercury-L-cysteine complex is a substrate for human L-type large neutral amino acid transporter (LAT) 1 and LAT2. · 2002 · https://pubmed.ncbi.nlm.nih.gov/12117417/ · DOI 10.1042/BJ20020841

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

CaSR-null compared with wild-type primary mouse intestinal I cells.

limitations

This is receptor failure, not phenylalanine or calcium dietary deficiency.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Removing one sensor disables that route without disabling every secretion trigger.

primary_references

The extracellular calcium-sensing receptor is required for cholecystokinin secretion in response to L-phenylalanine in acutely isolated intestinal I cells. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21252045/ · DOI 10.1152/ajpgi.00342.2010

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 286–292

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · CaSR-null compared with wild-type primary mouse intestinal I cells. · source_derived_draft · unverified_draft

## l-phenylalanine-casr-loss Removing one sensor disables that route without disabling every secretion trigger. CaSR knockout abolished the phenylalanine-evoked calcium response in primary mouse I cells and prevented the normal stimulatory CCK response; responses to KCl and tryptone were preserved. Model: CaSR-null compared with wild-type primary mouse intestinal I cells. Limitations: This is receptor failure, not phenylalanine or calcium dietary deficiency. Evidence access: Primary abstract The extracellular calcium-sensing receptor is required for cholecystokinin secretion in response to L-phenylalanine in acutely isolated intestinal I cells. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21252045/ · DOI 10.1152/ajpgi.00342.2010

evidence_access

Primary abstract

experimental_model

In-vitro human cytosolic and mitochondrial synthetase assays.

limitations

Assay mischarging does not establish clinical proteotoxicity from a usual phenylalanine intake.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Similar-looking molecules can challenge protein-building accuracy.

primary_references

Bacterial and eukaryotic phenylalanyl-tRNA synthetases catalyze misaminoacylation of tRNA(Phe) with 3,4-dihydroxy-L-phenylalanine. · 2011 · https://pubmed.ncbi.nlm.nih.gov/22035791/ · DOI 10.1016/j.chembiol.2011.08.008

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 134–140

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · In-vitro human cytosolic and mitochondrial synthetase assays. · source_derived_draft · unverified_draft

## l-phenylalanine-charging-fidelity Similar-looking molecules can challenge protein-building accuracy. Human cytosolic and mitochondrial phenylalanyl-tRNA synthetases could mischarge L-DOPA in biochemical assays; cytosolic editing hydrolyzed L-DOPA- and tyrosine-mischarged tRNA, whereas the mitochondrial system discriminated less effectively. Model: In-vitro human cytosolic and mitochondrial synthetase assays. Limitations: Assay mischarging does not establish clinical proteotoxicity from a usual phenylalanine intake. Evidence access: Primary abstract Bacterial and eukaryotic phenylalanyl-tRNA synthetases catalyze misaminoacylation of tRNA(Phe) with 3,4-dihydroxy-L-phenylalanine. · 2011 · https://pubmed.ncbi.nlm.nih.gov/22035791/ · DOI 10.1016/j.chembiol.2011.08.008

evidence_access

Primary abstract

experimental_model

Human phenylalanyl-tRNA synthetase biochemical comparison.

limitations

This aminoacylation function is distinct from conversion of phenylalanine to tyrosine.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Protein construction needs a molecular loading and proofreading system.

primary_references

Bacterial and eukaryotic phenylalanyl-tRNA synthetases catalyze misaminoacylation of tRNA(Phe) with 3,4-dihydroxy-L-phenylalanine. · 2011 · https://pubmed.ncbi.nlm.nih.gov/22035791/ · DOI 10.1016/j.chembiol.2011.08.008

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 126–132

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human phenylalanyl-tRNA synthetase biochemical comparison. · source_derived_draft · unverified_draft

## l-phenylalanine-cytosolic-charging Protein construction needs a molecular loading and proofreading system. Human cytosolic phenylalanyl-tRNA synthetase activates phenylalanine and attaches it to tRNA(Phe), with editing that discriminates against mischarged aromatic amino acids. Model: Human phenylalanyl-tRNA synthetase biochemical comparison. Limitations: This aminoacylation function is distinct from conversion of phenylalanine to tyrosine. Evidence access: Primary abstract Bacterial and eukaryotic phenylalanyl-tRNA synthetases catalyze misaminoacylation of tRNA(Phe) with 3,4-dihydroxy-L-phenylalanine. · 2011 · https://pubmed.ncbi.nlm.nih.gov/22035791/ · DOI 10.1016/j.chembiol.2011.08.008

evidence_access

Primary abstract

experimental_model

Human DNAJC12 deficiency study with functional interaction experiments.

limitations

Interaction does not imply identical effects in all tissues or rescue by extra substrate.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A shared chaperone supports several amino-acid processing enzymes.

primary_references

Biallelic Mutations in DNAJC12 Cause Hyperphenylalaninemia, Dystonia, and Intellectual Disability. · 2017 · https://pubmed.ncbi.nlm.nih.gov/28132689/ · DOI 10.1016/j.ajhg.2017.01.002

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 102–108

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human DNAJC12 deficiency study with functional interaction experiments. · source_derived_draft · unverified_draft

## l-phenylalanine-dnaj-chaperone A shared chaperone supports several amino-acid processing enzymes. DNAJC12 interacted with aromatic amino-acid hydroxylases, including PAH, tyrosine hydroxylase and tryptophan hydroxylases. Model: Human DNAJC12 deficiency study with functional interaction experiments. Limitations: Interaction does not imply identical effects in all tissues or rescue by extra substrate. Evidence access: Primary abstract Biallelic Mutations in DNAJC12 Cause Hyperphenylalaninemia, Dystonia, and Intellectual Disability. · 2017 · https://pubmed.ncbi.nlm.nih.gov/28132689/ · DOI 10.1016/j.ajhg.2017.01.002

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Human genetic case series and functional experiments.

limitations

Early combined BH4/neurotransmitter-precursor treatment was not a controlled test of phenylalanine supplementation.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Phenylalanine can accumulate because its supporting machinery is defective.

primary_references

Biallelic Mutations in DNAJC12 Cause Hyperphenylalaninemia, Dystonia, and Intellectual Disability. · 2017 · https://pubmed.ncbi.nlm.nih.gov/28132689/ · DOI 10.1016/j.ajhg.2017.01.002

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 110–116

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human genetic case series and functional experiments. · source_derived_draft · unverified_draft

## l-phenylalanine-dnaj-failure Phenylalanine can accumulate because its supporting machinery is defective. Biallelic DNAJC12 variants in six patients from four families accompanied hyperphenylalaninemia and neurotransmitter abnormalities; functional studies found reduced PAH activity. Model: Human genetic case series and functional experiments. Limitations: Early combined BH4/neurotransmitter-precursor treatment was not a controlled test of phenylalanine supplementation. Evidence access: Primary abstract Biallelic Mutations in DNAJC12 Cause Hyperphenylalaninemia, Dystonia, and Intellectual Disability. · 2017 · https://pubmed.ncbi.nlm.nih.gov/28132689/ · DOI 10.1016/j.ajhg.2017.01.002

evidence_access

Primary abstract

experimental_model

Human purified proteins, crystallography and binding/kinetic studies.

limitations

Cofactor synthesis has additional steps; structural regulation does not establish a clinical depletion or supplementation effect.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Cofactor production has both a demand signal and a feedback brake.

primary_references

Biophysical and structural investigation of the regulation of human GTP cyclohydrolase I by its regulatory protein GFRP. · 2021 · https://pubmed.ncbi.nlm.nih.gov/33387654/ · DOI 10.1016/j.jsb.2020.107691

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 46–52

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human purified proteins, crystallography and binding/kinetic studies. · source_derived_draft · unverified_draft

## l-phenylalanine-gch1-feedback Cofactor production has both a demand signal and a feedback brake. BH4 and phenylalanine favored inhibited and activated human GCH1-GFRP complexes, respectively; ligand-dependent conformational changes stabilized binding. Model: Human purified proteins, crystallography and binding/kinetic studies. Limitations: Cofactor synthesis has additional steps; structural regulation does not establish a clinical depletion or supplementation effect. Evidence access: Primary abstract Biophysical and structural investigation of the regulation of human GTP cyclohydrolase I by its regulatory protein GFRP. · 2021 · https://pubmed.ncbi.nlm.nih.gov/33387654/ · DOI 10.1016/j.jsb.2020.107691

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary full text

experimental_model

Mouse receptor-knockout whole-animal and islet experiments.

limitations

This differs from the study tryptophan result; it does not negate GPR142 signaling in a different cell model.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A receptor that responds in a dish may not be essential for the overall response.

primary_references

GPR142 Controls Tryptophan-Induced Insulin and Incretin Hormone Secretion to Improve Glucose Metabolism. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27322810/ · DOI 10.1371/journal.pone.0157298

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 302–308

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Mouse receptor-knockout whole-animal and islet experiments. · source_derived_draft · unverified_draft

## l-phenylalanine-gpr142-dispensability A receptor that responds in a dish may not be essential for the overall response. Phenylalanine-associated glucose-tolerance improvement persisted in Gpr142-knockout mice, and its modest islet insulin response was not significantly different between knockout and wild-type mice. Model: Mouse receptor-knockout whole-animal and islet experiments. Limitations: This differs from the study tryptophan result; it does not negate GPR142 signaling in a different cell model. Evidence access: Primary full text GPR142 Controls Tryptophan-Induced Insulin and Incretin Hormone Secretion to Improve Glucose Metabolism. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27322810/ · DOI 10.1371/journal.pone.0157298

evidence_access

Primary full text

experimental_model

Human/mouse metabolomics study; established conjugation route described in primary full text.

limitations

This is not a purified conjugating-enzyme kinetic experiment and does not show clinically meaningful glutamine or glycine depletion.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Host amino acids help turn a bacterial product into circulating metabolites.

primary_references

A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 358–364

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human/mouse metabolomics study; established conjugation route described in primary full text. · source_derived_draft · unverified_draft

## l-phenylalanine-host-conjugation Host amino acids help turn a bacterial product into circulating metabolites. Host conjugation of microbially derived phenylacetate with glutamine produces PAGln, the predominant human conjugate in the study; glycine conjugation produces PAGly, predominant in mice. Model: Human/mouse metabolomics study; established conjugation route described in primary full text. Limitations: This is not a purified conjugating-enzyme kinetic experiment and does not show clinically meaningful glutamine or glycine depletion. Evidence access: Primary full text A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

evidence_access

Primary abstract

experimental_model

Human THP-1 cells; interferon-gamma alone compared with interferon-gamma plus LPS.

limitations

Pteridine output is not synonymous with bioavailable BH4; no clinical inflammatory threshold is defined.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Inflammatory stimulation changed how this cell model responded to phenylalanine.

primary_references

Bacterial lipopolysaccharide down-regulates expression of GTP cyclohydrolase I feedback regulatory protein. · 2002 · https://pubmed.ncbi.nlm.nih.gov/11799107/ · DOI 10.1074/jbc.M107326200

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 54–60

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human THP-1 cells; interferon-gamma alone compared with interferon-gamma plus LPS. · source_derived_draft · unverified_draft

## l-phenylalanine-inflammation-feedback Inflammatory stimulation changed how this cell model responded to phenylalanine. LPS at 1 microgram/mL reduced GFRP expression in human THP-1 cells; with interferon-gamma plus LPS, pteridine production became phenylalanine-independent. Model: Human THP-1 cells; interferon-gamma alone compared with interferon-gamma plus LPS. Limitations: Pteridine output is not synonymous with bioavailable BH4; no clinical inflammatory threshold is defined. Evidence access: Primary abstract Bacterial lipopolysaccharide down-regulates expression of GTP cyclohydrolase I feedback regulatory protein. · 2002 · https://pubmed.ncbi.nlm.nih.gov/11799107/ · DOI 10.1074/jbc.M107326200

evidence_access

Primary full text

experimental_model

Human metabolomics and endurance/sprint/resistance comparisons.

limitations

A biomarker rise is not evidence that taking phenylalanine reproduces exercise benefits.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Phenylalanine can join lactate in a metabolite that rises after exercise.

primary_references

An exercise-inducible metabolite that suppresses feeding and obesity. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35705806/ · DOI 10.1038/s41586-022-04828-5

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 398–404

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human metabolomics and endurance/sprint/resistance comparisons. · source_derived_draft · unverified_draft

## l-phenylalanine-lacphe-exercise Phenylalanine can join lactate in a metabolite that rises after exercise. Lac-Phe rose after exercise in human cohorts of 36 and 8 participants; in the modality comparison, changes tracked lactate and were greatest after sprint exercise. Model: Human metabolomics and endurance/sprint/resistance comparisons. Limitations: A biomarker rise is not evidence that taking phenylalanine reproduces exercise benefits. Evidence access: Primary full text An exercise-inducible metabolite that suppresses feeding and obesity. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35705806/ · DOI 10.1038/s41586-022-04828-5

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary full text

experimental_model

Mouse global Cndp2 knockout; repeated treadmill exercise with high-fat feeding.

limitations

Cndp2 has other substrates; the phenotype was conditional on exercise and diet and did not establish a human deficiency syndrome.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Removing a production enzyme weakened one part of the exercise response.

primary_references

An exercise-inducible metabolite that suppresses feeding and obesity. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35705806/ · DOI 10.1038/s41586-022-04828-5

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 414–420

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Mouse global Cndp2 knockout; repeated treadmill exercise with high-fat feeding. · source_derived_draft · unverified_draft

## l-phenylalanine-lacphe-genetic Removing a production enzyme weakened one part of the exercise response. Global Cndp2 knockout markedly reduced circulating Lac-Phe and attenuated the food-intake and weight response to chronic exercise on a high-fat diet. Model: Mouse global Cndp2 knockout; repeated treadmill exercise with high-fat feeding. Limitations: Cndp2 has other substrates; the phenotype was conditional on exercise and diet and did not establish a human deficiency syndrome. Evidence access: Primary full text An exercise-inducible metabolite that suppresses feeding and obesity. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35705806/ · DOI 10.1038/s41586-022-04828-5

evidence_access

Primary full text

experimental_model

Intraperitoneal pharmacological dosing in diet-induced obese mice.

limitations

Oral dosing did not reproduce the effect; lean mice did not respond even up to 150 mg/kg. Lactate and phenylalanine separately did not reproduce it.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

The combined metabolite changed feeding in a specific mouse model.

primary_references

An exercise-inducible metabolite that suppresses feeding and obesity. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35705806/ · DOI 10.1038/s41586-022-04828-5

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 406–412

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Intraperitoneal pharmacological dosing in diet-induced obese mice. · source_derived_draft · unverified_draft

## l-phenylalanine-lacphe-obese-mice The combined metabolite changed feeding in a specific mouse model. Injected Lac-Phe at 50 mg/kg reduced food intake in diet-induced obese mice; daily injection for ten days reduced intake, adiposity and weight. Model: Intraperitoneal pharmacological dosing in diet-induced obese mice. Limitations: Oral dosing did not reproduce the effect; lean mice did not respond even up to 150 mg/kg. Lactate and phenylalanine separately did not reproduce it. Evidence access: Primary full text An exercise-inducible metabolite that suppresses feeding and obesity. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35705806/ · DOI 10.1038/s41586-022-04828-5

evidence_access

Primary abstract

experimental_model

Four two-week crossover phases involving LNAA/placebo with or without medical product.

limitations

Small, short study; not a replacement recommendation for established PKU management.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A mixture can change outcomes, but the existing diet affects its added value.

primary_references

The effects of large neutral amino acid supplements in PKU: an MRS and neuropsychological study. · 2007 · https://pubmed.ncbi.nlm.nih.gov/17368065/ · DOI 10.1016/j.ymgme.2007.02.002

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 206–212

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Four two-week crossover phases involving LNAA/placebo with or without medical product. · source_derived_draft · unverified_draft

## l-phenylalanine-lnaa-clinical-boundary A mixture can change outcomes, but the existing diet affects its added value. In a 16-person PKU crossover study, LNAA supplementation produced limited executive-function benefits and lowered plasma phenylalanine mainly when participants were not taking their usual medical product. Model: Four two-week crossover phases involving LNAA/placebo with or without medical product. Limitations: Small, short study; not a replacement recommendation for established PKU management. Evidence access: Primary abstract The effects of large neutral amino acid supplements in PKU: an MRS and neuropsychological study. · 2007 · https://pubmed.ncbi.nlm.nih.gov/17368065/ · DOI 10.1016/j.ymgme.2007.02.002

evidence_access

Primary full text

experimental_model

Three three-week crossover periods; serum/urine melatonin, urinary dopamine and plasma amino-acid ratios.

limitations

Urinary dopamine and melatonin are surrogate readouts, not a direct demonstration of restored brain neurotransmitter concentrations.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A downstream marker can improve even when phenylalanine concentration stays similar.

primary_references

Large neutral amino acid supplementation increases melatonin synthesis in phenylketonuria: a new biomarker. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23164313/ · DOI 10.1016/j.jpeds.2012.10.015

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 214–220

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Three three-week crossover periods; serum/urine melatonin, urinary dopamine and plasma amino-acid ratios. · source_derived_draft · unverified_draft

## l-phenylalanine-lnaa-monoamine-markers A downstream marker can improve even when phenylalanine concentration stays similar. In ten adults with PKU, LNAA supplementation increased melatonin measures and urinary dopamine while phenylalanine itself did not significantly change. Model: Three three-week crossover periods; serum/urine melatonin, urinary dopamine and plasma amino-acid ratios. Limitations: Urinary dopamine and melatonin are surrogate readouts, not a direct demonstration of restored brain neurotransmitter concentrations. Evidence access: Primary full text Large neutral amino acid supplementation increases melatonin synthesis in phenylketonuria: a new biomarker. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23164313/ · DOI 10.1016/j.jpeds.2012.10.015

evidence_access

Primary full text

experimental_model

C. sporogenes mutant culture and metabolite measurements.

limitations

A branch in one organism is not a fixed whole-microbiome fate map.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Which microbial enzymes are present can change which metabolite is produced.

primary_references

A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 350–356

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · C. sporogenes mutant culture and metabolite measurements. · source_derived_draft · unverified_draft

## l-phenylalanine-microbial-branch Which microbial enzymes are present can change which metabolite is produced. The C. sporogenes FldH-dependent reductive aromatic-amino-acid branch competed with the PorA-associated oxidative branch; gene perturbations changed phenylacetate versus phenylpropionate output. Model: C. sporogenes mutant culture and metabolite measurements. Limitations: A branch in one organism is not a fixed whole-microbiome fate map. Evidence access: Primary full text A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

evidence_access

Primary full text

experimental_model

Human antibiotic suppression and post-antibiotic recovery sampling at least three weeks later.

limitations

Antibiotics affect many microbes and metabolites; this does not isolate one bacterial enzyme or recommend antimicrobial use.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

The human circulating metabolite depends in part on gut microbial activity.

primary_references

A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 366–372

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human antibiotic suppression and post-antibiotic recovery sampling at least three weeks later. · source_derived_draft · unverified_draft

## l-phenylalanine-microbial-human-dependence The human circulating metabolite depends in part on gut microbial activity. Seven days of broad-spectrum antibiotics in fifteen subjects markedly reduced circulating PAGln, with recovery after microbial repopulation. Model: Human antibiotic suppression and post-antibiotic recovery sampling at least three weeks later. Limitations: Antibiotics affect many microbes and metabolites; this does not isolate one bacterial enzyme or recommend antimicrobial use. Evidence access: Primary full text A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

evidence_access

Primary full text

experimental_model

Defined bacterial cultures and stable-isotope experiments; 100 micromolar labeled phenylalanine over 24 hours.

limitations

Bacterial flux is strain- and environment-dependent; no human dietary conversion fraction is established.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Some gut bacteria send phenylalanine into a different metabolic route.

primary_references

A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 342–348

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Defined bacterial cultures and stable-isotope experiments; 100 micromolar labeled phenylalanine over 24 hours. · source_derived_draft · unverified_draft

## l-phenylalanine-microbial-oxidation Some gut bacteria send phenylalanine into a different metabolic route. Clostridium sporogenes porA disruption reduced the oxidative conversion of phenylalanine-derived carbon to phenylacetate; labeled phenylalanine tracing supported the pathway through phenylpyruvate. Model: Defined bacterial cultures and stable-isotope experiments; 100 micromolar labeled phenylalanine over 24 hours. Limitations: Bacterial flux is strain- and environment-dependent; no human dietary conversion fraction is established. Evidence access: Primary full text A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary full text

experimental_model

Heart-specific Fars2-deficient mice and mitochondrial translation assays.

limitations

Genetic enzyme loss is not the same as inadequate dietary phenylalanine; human variant binding predictions were not direct kinetic measurements.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Mitochondria need their own phenylalanine-loading enzyme.

primary_references

FARS2 Deficiency Causes Cardiomyopathy by Disrupting Mitochondrial Homeostasis and the Mitochondrial Quality Control System. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38362779/ · DOI 10.1161/CIRCULATIONAHA.123.064489

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 142–148

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Heart-specific Fars2-deficient mice and mitochondrial translation assays. · source_derived_draft · unverified_draft

## l-phenylalanine-mitochondrial-charging Mitochondria need their own phenylalanine-loading enzyme. Cardiac Fars2 deficiency impaired mitochondrial tRNA(Phe) aminoacylation and mitochondrial protein synthesis in mice. Model: Heart-specific Fars2-deficient mice and mitochondrial translation assays. Limitations: Genetic enzyme loss is not the same as inadequate dietary phenylalanine; human variant binding predictions were not direct kinetic measurements. Evidence access: Primary full text FARS2 Deficiency Causes Cardiomyopathy by Disrupting Mitochondrial Homeostasis and the Mitochondrial Quality Control System. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38362779/ · DOI 10.1161/CIRCULATIONAHA.123.064489

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary full text

experimental_model

Neonatal rat ventricular myocyte knockdown assays.

limitations

These are related cellular readouts, not proof of human niacin or phenylalanine deficiency.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

The downstream effects include both energy production and redox balance.

primary_references

FARS2 Deficiency Causes Cardiomyopathy by Disrupting Mitochondrial Homeostasis and the Mitochondrial Quality Control System. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38362779/ · DOI 10.1161/CIRCULATIONAHA.123.064489

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 158–164

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Neonatal rat ventricular myocyte knockdown assays. · source_derived_draft · unverified_draft

## l-phenylalanine-mitochondrial-energy The downstream effects include both energy production and redox balance. Fars2 knockdown in neonatal rat ventricular myocytes lowered ATP and mitochondrial membrane potential, increased ROS, and reduced the NAD+/NADH ratio. Model: Neonatal rat ventricular myocyte knockdown assays. Limitations: These are related cellular readouts, not proof of human niacin or phenylalanine deficiency. Evidence access: Primary full text FARS2 Deficiency Causes Cardiomyopathy by Disrupting Mitochondrial Homeostasis and the Mitochondrial Quality Control System. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38362779/ · DOI 10.1161/CIRCULATIONAHA.123.064489

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary full text

experimental_model

Conditional mouse cardiac Fars2 knockout; separate R415L model also studied.

limitations

No evidence here that phenylalanine supplements rescue the genetic defect.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Failure at the protein-loading step can affect an organ that needs substantial energy.

primary_references

FARS2 Deficiency Causes Cardiomyopathy by Disrupting Mitochondrial Homeostasis and the Mitochondrial Quality Control System. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38362779/ · DOI 10.1161/CIRCULATIONAHA.123.064489

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 150–156

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Conditional mouse cardiac Fars2 knockout; separate R415L model also studied. · source_derived_draft · unverified_draft

## l-phenylalanine-mitochondrial-heart Failure at the protein-loading step can affect an organ that needs substantial energy. Heart-specific Fars2 loss produced hypertrophy, ventricular dilation and progressive cardiac failure with mitochondrial dysfunction. Model: Conditional mouse cardiac Fars2 knockout; separate R415L model also studied. Limitations: No evidence here that phenylalanine supplements rescue the genetic defect. Evidence access: Primary full text FARS2 Deficiency Causes Cardiomyopathy by Disrupting Mitochondrial Homeostasis and the Mitochondrial Quality Control System. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38362779/ · DOI 10.1161/CIRCULATIONAHA.123.064489

evidence_access

Primary full text

experimental_model

Human MEG-01 receptor knockdown and HEK293 receptor-expression experiments, with pharmacologic comparisons.

limitations

Functional dependence is not proof of a single orthosteric binding mode or a clinical drug interaction.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

The platelet-related signal connects to receptors used by other physiological pathways.

primary_references

A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 382–388

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human MEG-01 receptor knockdown and HEK293 receptor-expression experiments, with pharmacologic comparisons. · source_derived_draft · unverified_draft

## l-phenylalanine-pagln-adrenergic The platelet-related signal connects to receptors used by other physiological pathways. Knockdown and overexpression experiments implicated ADRA2A, ADRA2B and ADRB2 in PAGln-associated signaling, supporting an adrenergic-receptor-dependent route. Model: Human MEG-01 receptor knockdown and HEK293 receptor-expression experiments, with pharmacologic comparisons. Limitations: Functional dependence is not proof of a single orthosteric binding mode or a clinical drug interaction. Evidence access: Primary full text A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

evidence_access

Primary full text

experimental_model

Human clinical cohorts; three-year event follow-up.

limitations

Residual confounding and renal clearance matter; no randomized dietary phenylalanine intervention establishes causation.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A blood association identifies a research signal, not the cause by itself.

primary_references

A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 390–396

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human clinical cohorts; three-year event follow-up. · source_derived_draft · unverified_draft

## l-phenylalanine-pagln-outcomes A blood association identifies a research signal, not the cause by itself. Circulating PAGln was associated with cardiovascular disease and subsequent major adverse cardiovascular events in discovery and validation cohorts of 1162 and 4000 subjects. Model: Human clinical cohorts; three-year event follow-up. Limitations: Residual confounding and renal clearance matter; no randomized dietary phenylalanine intervention establishes causation. Evidence access: Primary full text A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

evidence_access

Primary full text

experimental_model

Isolated human platelets; agonist-challenge experiments.

limitations

Metabolite exposure is not phenylalanine exposure; this does not establish that dietary phenylalanine causes thrombosis.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A downstream microbial-host metabolite can alter platelet responsiveness in an assay.

primary_references

A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 374–380

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Isolated human platelets; agonist-challenge experiments. · source_derived_draft · unverified_draft

## l-phenylalanine-pagln-platelets A downstream microbial-host metabolite can alter platelet responsiveness in an assay. PAGln at 100 micromolar for 30 minutes enhanced agonist-induced human platelet responses, including calcium signaling. Model: Isolated human platelets; agonist-challenge experiments. Limitations: Metabolite exposure is not phenylalanine exposure; this does not establish that dietary phenylalanine causes thrombosis. Evidence access: Primary full text A Cardiovascular Disease-Linked Gut Microbial Metabolite Acts via Adrenergic Receptors. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32142679/ · DOI 10.1016/j.cell.2020.02.016

evidence_access

Primary full text; reaction background distinguished from new structural experiments

experimental_model

Human PAH structural study; established reaction described in the full-text introduction.

limitations

This record describes the established reaction, not a new dietary intervention or a human iron-deficiency threshold.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Making tyrosine requires a working enzyme and its chemical helpers.

primary_references

Structural basis for ligand-dependent dimerization of phenylalanine hydroxylase regulatory domain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27049649/ · DOI 10.1038/srep23748

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 14–20

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human PAH structural study; established reaction described in the full-text introduction. · source_derived_draft · unverified_draft

## l-phenylalanine-pah-conversion Making tyrosine requires a working enzyme and its chemical helpers. PAH catalyzes phenylalanine hydroxylation to tyrosine using BH4, molecular oxygen and non-heme ferrous iron. Model: Human PAH structural study; established reaction described in the full-text introduction. Limitations: This record describes the established reaction, not a new dietary intervention or a human iron-deficiency threshold. Evidence access: Primary full text; reaction background distinguished from new structural experiments Structural basis for ligand-dependent dimerization of phenylalanine hydroxylase regulatory domain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27049649/ · DOI 10.1038/srep23748

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary full text

experimental_model

Purified human PAH regulatory-domain E76A comparison.

limitations

Domain behavior does not quantify whole-body phenylalanine clearance for every PAH variant.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A PAH variant can damage the substrate-sensing switch.

primary_references

Structural basis for ligand-dependent dimerization of phenylalanine hydroxylase regulatory domain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27049649/ · DOI 10.1038/srep23748

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 30–36

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Purified human PAH regulatory-domain E76A comparison. · source_derived_draft · unverified_draft

## l-phenylalanine-pah-variant A PAH variant can damage the substrate-sensing switch. The disease-associated E76A regulatory-domain mutant showed reduced phenylalanine binding, dimerization and stability. Model: Purified human PAH regulatory-domain E76A comparison. Limitations: Domain behavior does not quantify whole-body phenylalanine clearance for every PAH variant. Evidence access: Primary full text Structural basis for ligand-dependent dimerization of phenylalanine hydroxylase regulatory domain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/27049649/ · DOI 10.1038/srep23748

evidence_access

Primary abstract

experimental_model

Enzyme mechanism described in the primary PRISM clinical report.

limitations

Lowering phenylalanine through this bypass does not restore the PAH-to-tyrosine reaction.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A drug can remove the accumulating substrate through a different chemical route.

primary_references

Pegvaliase for the treatment of phenylketonuria: Results of a long-term phase 3 clinical trial program (PRISM). · 2018 · https://pubmed.ncbi.nlm.nih.gov/29653686/ · DOI 10.1016/j.ymgme.2018.03.006

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 238–244

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Enzyme mechanism described in the primary PRISM clinical report. · source_derived_draft · unverified_draft

## l-phenylalanine-pal-bypass A drug can remove the accumulating substrate through a different chemical route. Pegvaliase supplies a PEGylated microbial phenylalanine ammonia lyase pathway that converts phenylalanine to trans-cinnamate and ammonia rather than tyrosine. Model: Enzyme mechanism described in the primary PRISM clinical report. Limitations: Lowering phenylalanine through this bypass does not restore the PAH-to-tyrosine reaction. Evidence access: Primary abstract Pegvaliase for the treatment of phenylketonuria: Results of a long-term phase 3 clinical trial program (PRISM). · 2018 · https://pubmed.ncbi.nlm.nih.gov/29653686/ · DOI 10.1016/j.ymgme.2018.03.006

evidence_access

Primary abstract

experimental_model

Adult phase-3 clinical program with long-term titrated exposure.

limitations

Immune-mediated adverse events matter: 17 events in 12 participants met acute systemic hypersensitivity/anaphylaxis criteria. This is not dietary enzyme use.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

The bypass can lower blood phenylalanine, but has its own treatment risks.

primary_references

Pegvaliase for the treatment of phenylketonuria: Results of a long-term phase 3 clinical trial program (PRISM). · 2018 · https://pubmed.ncbi.nlm.nih.gov/29653686/ · DOI 10.1016/j.ymgme.2018.03.006

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 246–252

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Adult phase-3 clinical program with long-term titrated exposure. · source_derived_draft · unverified_draft

## l-phenylalanine-pal-clinical The bypass can lower blood phenylalanine, but has its own treatment risks. PRISM studies in 261 adults with PAH deficiency found substantial phenylalanine reductions during induction, titration and maintenance pegvaliase treatment. Model: Adult phase-3 clinical program with long-term titrated exposure. Limitations: Immune-mediated adverse events matter: 17 events in 12 participants met acute systemic hypersensitivity/anaphylaxis criteria. This is not dietary enzyme use. Evidence access: Primary abstract Pegvaliase for the treatment of phenylketonuria: Results of a long-term phase 3 clinical trial program (PRISM). · 2018 · https://pubmed.ncbi.nlm.nih.gov/29653686/ · DOI 10.1016/j.ymgme.2018.03.006

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Small human case series, three adults with homozygous PCBD1 mutations.

limitations

Two also had MODY-like diabetes regardless of magnesium status; neither finding establishes that phenylalanine supplements cause or correct the disorder.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A genetic defect can connect abnormal phenylalanine handling with magnesium wasting.

primary_references

Mutations in PCBD1 cause hypomagnesemia and renal magnesium wasting. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24204001/ · DOI 10.1681/ASN.2013040337

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 94–100

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Small human case series, three adults with homozygous PCBD1 mutations. · source_derived_draft · unverified_draft

## l-phenylalanine-pcbd-magnesium A genetic defect can connect abnormal phenylalanine handling with magnesium wasting. Two of three adults with homozygous PCBD1 mutations had hypomagnesemia with renal magnesium loss. Model: Small human case series, three adults with homozygous PCBD1 mutations. Limitations: Two also had MODY-like diabetes regardless of magnesium status; neither finding establishes that phenylalanine supplements cause or correct the disorder. Evidence access: Primary abstract Mutations in PCBD1 cause hypomagnesemia and renal magnesium wasting. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24204001/ · DOI 10.1681/ASN.2013040337

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Human PCBD1 variant expression and promoter assays.

limitations

Variant effects are not uniform and do not establish dietary phenylalanine deficiency.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Some mutations damage the protein and weaken its kidney-related transcriptional function.

primary_references

Mutations in PCBD1 cause hypomagnesemia and renal magnesium wasting. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24204001/ · DOI 10.1681/ASN.2013040337

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 86–92

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human PCBD1 variant expression and promoter assays. · source_derived_draft · unverified_draft

## l-phenylalanine-pcbd-mutants Some mutations damage the protein and weaken its kidney-related transcriptional function. Five of seven tested PCBD1 mutations caused proteolytic instability and reduced FXYD2 promoter activity. Model: Human PCBD1 variant expression and promoter assays. Limitations: Variant effects are not uniform and do not establish dietary phenylalanine deficiency. Evidence access: Primary abstract Mutations in PCBD1 cause hypomagnesemia and renal magnesium wasting. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24204001/ · DOI 10.1681/ASN.2013040337

evidence_access

Primary abstract

experimental_model

Human PCBD1 mutation study; established biochemical role and disease background.

limitations

The renal study does not directly measure whole-body BH4 recycling flux. The transcriptional role below is separately recorded.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

One cofactor-recycling protein has another important job in the kidney.

primary_references

Mutations in PCBD1 cause hypomagnesemia and renal magnesium wasting. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24204001/ · DOI 10.1681/ASN.2013040337

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 62–68

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human PCBD1 mutation study; established biochemical role and disease background. · source_derived_draft · unverified_draft

## l-phenylalanine-pcbd-recycling-role One cofactor-recycling protein has another important job in the kidney. PCBD1 has a pterin-carbinolamine dehydratase role in BH4 regeneration; biallelic defects are associated with transient neonatal hyperphenylalaninemia and primapterinuria. Model: Human PCBD1 mutation study; established biochemical role and disease background. Limitations: The renal study does not directly measure whole-body BH4 recycling flux. The transcriptional role below is separately recorded. Evidence access: Primary abstract Mutations in PCBD1 cause hypomagnesemia and renal magnesium wasting. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24204001/ · DOI 10.1681/ASN.2013040337

evidence_access

Primary abstract

experimental_model

Human kidney-cell overexpression and promoter assay.

limitations

Promoter activity is not a direct measurement of magnesium flux or proof that phenylalanine intake regulates magnesium.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A protein used in phenylalanine metabolism also helps control a kidney transport regulator.

primary_references

Mutations in PCBD1 cause hypomagnesemia and renal magnesium wasting. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24204001/ · DOI 10.1681/ASN.2013040337

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 78–84

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human kidney-cell overexpression and promoter assay. · source_derived_draft · unverified_draft

## l-phenylalanine-pcbd-transcription A protein used in phenylalanine metabolism also helps control a kidney transport regulator. Overexpressed wild-type PCBD1 bound HNF1B and increased FXYD2 promoter activity in a human kidney cell line. Model: Human kidney-cell overexpression and promoter assay. Limitations: Promoter activity is not a direct measurement of magnesium flux or proof that phenylalanine intake regulates magnesium. Evidence access: Primary abstract Mutations in PCBD1 cause hypomagnesemia and renal magnesium wasting. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24204001/ · DOI 10.1681/ASN.2013040337

evidence_access

Primary abstract

experimental_model

Human QDPR expressed in E. coli; enzyme purification, kinetic characterization and structure.

limitations

This binary structure alone does not show that niacin supplementation changes phenylalanine clearance.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

The cofactor-recycling network includes an NADH-binding enzyme.

primary_references

The crystallographic structure of a human dihydropteridine reductase NADH binary complex expressed in Escherichia coli by a cDNA constructed from its rat homologue. · 1993 · https://pubmed.ncbi.nlm.nih.gov/8262916/

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 70–76

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human QDPR expressed in E. coli; enzyme purification, kinetic characterization and structure. · source_derived_draft · unverified_draft

## l-phenylalanine-qdpr-nadh The cofactor-recycling network includes an NADH-binding enzyme. A catalytically characterized recombinant human dihydropteridine reductase was crystallized in complex with NADH at 2.5-angstrom resolution. Model: Human QDPR expressed in E. coli; enzyme purification, kinetic characterization and structure. Limitations: This binary structure alone does not show that niacin supplementation changes phenylalanine clearance. Evidence access: Primary abstract The crystallographic structure of a human dihydropteridine reductase NADH binary complex expressed in Escherichia coli by a cDNA constructed from its rat homologue. · 1993 · https://pubmed.ncbi.nlm.nih.gov/8262916/

evidence_access

Primary abstract

experimental_model

PKU-model mice; oral dosing, dose not specified in accessed abstract.

limitations

Human efficacy and effects on other neutral amino acids are not established here.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A transporter intervention can lower blood levels by increasing urinary loss.

primary_references

Structure-guided development of a potent human B0AT1 inhibitor effective in a mouse model of phenylketonuria. · 2026 · https://pubmed.ncbi.nlm.nih.gov/42350764/ · DOI 10.1038/s42003-026-10535-y

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 182–188

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · PKU-model mice; oral dosing, dose not specified in accessed abstract. · source_derived_draft · unverified_draft

## l-phenylalanine-renal-excretion A transporter intervention can lower blood levels by increasing urinary loss. Oral experimental B0AT1 inhibition increased urinary phenylalanine and lowered plasma phenylalanine in PKU-model mice. Model: PKU-model mice; oral dosing, dose not specified in accessed abstract. Limitations: Human efficacy and effects on other neutral amino acids are not established here. Evidence access: Primary abstract Structure-guided development of a potent human B0AT1 inhibitor effective in a mouse model of phenylketonuria. · 2026 · https://pubmed.ncbi.nlm.nih.gov/42350764/ · DOI 10.1038/s42003-026-10535-y

evidence_access

Primary abstract

experimental_model

Human transporter cryo-EM and human/mouse transport inhibition assays.

limitations

Compound identity is not resolved in the accessed abstract; this is experimental pharmacology, not a supplement recommendation.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Transport can be blocked at a site away from where the amino acid binds.

primary_references

Structure-guided development of a potent human B0AT1 inhibitor effective in a mouse model of phenylketonuria. · 2026 · https://pubmed.ncbi.nlm.nih.gov/42350764/ · DOI 10.1038/s42003-026-10535-y

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 174–180

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human transporter cryo-EM and human/mouse transport inhibition assays. · source_derived_draft · unverified_draft

## l-phenylalanine-renal-inhibition Transport can be blocked at a site away from where the amino acid binds. A designed inhibitor occupied an allosteric B0AT1 pocket about 17 angstroms from the substrate site, stabilized an outward-occluded state and blocked transport with submicromolar IC50. Model: Human transporter cryo-EM and human/mouse transport inhibition assays. Limitations: Compound identity is not resolved in the accessed abstract; this is experimental pharmacology, not a supplement recommendation. Evidence access: Primary abstract Structure-guided development of a potent human B0AT1 inhibitor effective in a mouse model of phenylketonuria. · 2026 · https://pubmed.ncbi.nlm.nih.gov/42350764/ · DOI 10.1038/s42003-026-10535-y

evidence_access

Primary abstract

experimental_model

Randomized human PKU study enriched through prior responsiveness assessment.

limitations

Not all PAH defects respond; trial dose is historical evidence, not individualized guidance.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Providing the pharmaceutical cofactor helped some patients, with substantial response variation.

primary_references

Efficacy of sapropterin dihydrochloride (tetrahydrobiopterin, 6R-BH4) for reduction of phenylalanine concentration in patients with phenylketonuria: a phase III randomised placebo-controlled study. · 2007 · https://pubmed.ncbi.nlm.nih.gov/17693179/ · DOI 10.1016/S0140-6736(07)61234-3

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 222–228

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Randomized human PKU study enriched through prior responsiveness assessment. · source_derived_draft · unverified_draft

## l-phenylalanine-sapropterin-response Providing the pharmaceutical cofactor helped some patients, with substantial response variation. In an 89-participant six-week PKU trial, sapropterin 10 mg/kg/day lowered mean phenylalanine by 236 micromol/L versus a 3 micromol/L rise with placebo; 44% versus 9% had at least a 30% reduction. Model: Randomized human PKU study enriched through prior responsiveness assessment. Limitations: Not all PAH defects respond; trial dose is historical evidence, not individualized guidance. Evidence access: Primary abstract Efficacy of sapropterin dihydrochloride (tetrahydrobiopterin, 6R-BH4) for reduction of phenylalanine concentration in patients with phenylketonuria: a phase III randomised placebo-controlled study. · 2007 · https://pubmed.ncbi.nlm.nih.gov/17693179/ · DOI 10.1016/S0140-6736(07)61234-3

evidence_access

Primary abstract

experimental_model

Ten-week randomized trial after responder selection.

limitations

Selected pediatric responders cannot represent all PKU patients.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

When processing capacity improves, a responsive patient may tolerate more dietary phenylalanine.

primary_references

Efficacy of sapropterin dihydrochloride in increasing phenylalanine tolerance in children with phenylketonuria: a phase III, randomized, double-blind, placebo-controlled study. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19261295/ · DOI 10.1016/j.jpeds.2008.11.040

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 230–236

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Ten-week randomized trial after responder selection. · source_derived_draft · unverified_draft

## l-phenylalanine-sapropterin-tolerance When processing capacity improves, a responsive patient may tolerate more dietary phenylalanine. In 46 preselected sapropterin-responsive children, 20 mg/kg/day allowed more supplemental dietary phenylalanine while maintaining study blood targets: 20.9 versus 2.9 mg/kg/day with placebo. Model: Ten-week randomized trial after responder selection. Limitations: Selected pediatric responders cannot represent all PKU patients. Evidence access: Primary abstract Efficacy of sapropterin dihydrochloride in increasing phenylalanine tolerance in children with phenylketonuria: a phase III, randomized, double-blind, placebo-controlled study. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19261295/ · DOI 10.1016/j.jpeds.2008.11.040

availability_state

biomarker_context Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Forty-eight-hour human study with tyrosine on day two and calculated transport estimates.

limitations

Brain influx was modeled, not directly measured; high phenylalanine and other competing amino acids remain part of the model.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

A blood rise after supplementation need not provide steady predicted brain delivery.

primary_references

Tyrosine supplementation in phenylketonuria: diurnal blood tyrosine levels and presumptive brain influx of tyrosine and other large neutral amino acids. · 2001 · https://pubmed.ncbi.nlm.nih.gov/11562623/ · DOI 10.1067/mpd.2001.117576

trigger_kind

biomarker_context Imported condition classification; unverified.

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 198–204

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Forty-eight-hour human study with tyrosine on day two and calculated transport estimates. · source_derived_draft · unverified_draft

## l-phenylalanine-tyrosine-brain-estimate A blood rise after supplementation need not provide steady predicted brain delivery. In ten PKU patients, 300 mg/kg/day tyrosine transiently raised calculated brain tyrosine influx from 27% to 90% of normal, but it remained below 70% for half the sampled period. Model: Forty-eight-hour human study with tyrosine on day two and calculated transport estimates. Limitations: Brain influx was modeled, not directly measured; high phenylalanine and other competing amino acids remain part of the model. Evidence access: Primary abstract Tyrosine supplementation in phenylketonuria: diurnal blood tyrosine levels and presumptive brain influx of tyrosine and other large neutral amino acids. · 2001 · https://pubmed.ncbi.nlm.nih.gov/11562623/ · DOI 10.1067/mpd.2001.117576

evidence_access

Primary abstract

experimental_model

Human TH variant study; established enzyme reaction described in the abstract.

limitations

This is a downstream connection, not evidence that oral phenylalanine predictably raises brain dopamine.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Producing tyrosine is only the first part of the route toward dopamine.

primary_references

Tyrosine hydroxylase variants influence protein expression, cellular localization, stability, enzymatic activity and the physical interaction between tyrosine hydroxylase and GTP cyclohydrolase 1. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38084654/ · DOI 10.1002/jimd.12690

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 118–124

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human TH variant study; established enzyme reaction described in the abstract. · source_derived_draft · unverified_draft

## l-phenylalanine-tyrosine-next-step Producing tyrosine is only the first part of the route toward dopamine. Human tyrosine hydroxylase catalyzes BH4-dependent tyrosine hydroxylation to L-DOPA, a downstream step in dopamine biosynthesis. Model: Human TH variant study; established enzyme reaction described in the abstract. Limitations: This is a downstream connection, not evidence that oral phenylalanine predictably raises brain dopamine. Evidence access: Primary abstract Tyrosine hydroxylase variants influence protein expression, cellular localization, stability, enzymatic activity and the physical interaction between tyrosine hydroxylase and GTP cyclohydrolase 1. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38084654/ · DOI 10.1002/jimd.12690

evidence_access

Primary abstract

experimental_model

Human tracer feeding study with phenylalanine intakes 7.2–40 mg/kg/day and excess tyrosine.

limitations

This conditional estimate is not a universal intake target or evidence that tyrosine replaces phenylalanine in proteins.

nutrient_topic

L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Phenylalanine

plain_language

Supplying tyrosine changes how much phenylalanine must be reserved for making it.

primary_references

The Phenylalanine Requirement of Elderly Men and Women Measured by Direct 13C Carbon Oxidation Method Is Similar to That of Young Adults. · 2019 · https://pubmed.ncbi.nlm.nih.gov/31271193/ · DOI 10.1093/jn/nxz137

L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19) · lines 262–268

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human tracer feeding study with phenylalanine intakes 7.2–40 mg/kg/day and excess tyrosine. · source_derived_draft · unverified_draft

## l-phenylalanine-tyrosine-sparing Supplying tyrosine changes how much phenylalanine must be reserved for making it. With excess tyrosine supplied, indicator-amino-acid oxidation in twelve older adults across 66 studies estimated mean phenylalanine requirement at 9.03 mg/kg/day and its upper 95% confidence limit at 15.9 mg/kg/day. Model: Human tracer feeding study with phenylalanine intakes 7.2–40 mg/kg/day and excess tyrosine. Limitations: This conditional estimate is not a universal intake target or evidence that tyrosine replaces phenylalanine in proteins. Evidence access: Primary abstract The Phenylalanine Requirement of Elderly Men and Women Measured by Direct 13C Carbon Oxidation Method Is Similar to That of Young Adults. · 2019 · https://pubmed.ncbi.nlm.nih.gov/31271193/ · DOI 10.1093/jn/nxz137

evidence_access

Primary abstract

experimental_model

Overnight-fasted rats receiving defined meals with different amino-acid mixtures.

limitations

Not a validated universal human threshold or proof that protein-rich meals worsen mood.

nutrient_topic

Tryptophan collection; molecular form, preparation, species, exposure and manipulation remain explicit. · L-Tryptophan

plain_language

A higher blood level need not mean more tryptophan reaches the brain.

primary_references

Acute reduction of brain serotonin and 5-HIAA following food consumption: correlation with the ratio of serum tryptophan to the sum of competing amino acids. · 1975 · https://pubmed.ncbi.nlm.nih.gov/1080186/ · DOI 10.1007/BF01256759

Tryptophan: transport, protein synthesis, neuroactive metabolites, NAD and microbial pathways (2026-09-19) · lines 58–64

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Overnight-fasted rats receiving defined meals with different amino-acid mixtures. · source_derived_draft · unverified_draft

## tryptophan-brain-competition A higher blood level need not mean more tryptophan reaches the brain. In rat meal experiments, brain tryptophan and 5-hydroxyindoles tracked the serum tryptophan-to-competing-neutral-amino-acid ratio better than serum tryptophan alone. Model: Overnight-fasted rats receiving defined meals with different amino-acid mixtures. Limitations: Not a validated universal human threshold or proof that protein-rich meals worsen mood. Evidence access: Primary abstract Acute reduction of brain serotonin and 5-HIAA following food consumption: correlation with the ratio of serum tryptophan to the sum of competing amino acids. · 1975 · https://pubmed.ncbi.nlm.nih.gov/1080186/ · DOI 10.1007/BF01256759

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary full text, Figures 1–3

experimental_model

C. sporogenes ClosTron mutant and LC–MS/MS.

limitations

The mutation affects phenylalanine and tyrosine products as well; effects cannot all be assigned to indolepropionate.

nutrient_topic

Tryptophan collection; molecular form, preparation, species, exposure and manipulation remain explicit. · L-Tryptophan

plain_language

A missing microbial enzyme stopped production despite available tryptophan.

primary_references

A gut bacterial pathway metabolizes aromatic amino acids into nine circulating metabolites. · 2017 · https://pubmed.ncbi.nlm.nih.gov/29168502/ · DOI 10.1038/nature24661

trigger_kind

machinery_impairment Imported condition classification; unverified.

Tryptophan: transport, protein synthesis, neuroactive metabolites, NAD and microbial pathways (2026-09-19) · lines 490–496

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · C. sporogenes ClosTron mutant and LC–MS/MS. · source_derived_draft · unverified_draft

## tryptophan-fldc-loss A missing microbial enzyme stopped production despite available tryptophan. Disrupting fldC in C. sporogenes abolished indolepropionate accumulation in culture and altered aromatic-amino-acid metabolism. Model: C. sporogenes ClosTron mutant and LC–MS/MS. Limitations: The mutation affects phenylalanine and tyrosine products as well; effects cannot all be assigned to indolepropionate. Evidence access: Primary full text, Figures 1–3 A gut bacterial pathway metabolizes aromatic amino acids into nine circulating metabolites. · 2017 · https://pubmed.ncbi.nlm.nih.gov/29168502/ · DOI 10.1038/nature24661

evidence_access

Primary abstract

experimental_model

Human cloned transporter; expression strongest in kidney and intestine.

limitations

The paper proposes disease relevance; it does not establish TAT1 defects as the cause of blue diaper syndrome.

nutrient_topic

Tryptophan collection; molecular form, preparation, species, exposure and manipulation remain explicit. · L-Tryptophan

plain_language

Tryptophan also has an aromatic-amino-acid transport route.

primary_references

The human T-type amino acid transporter-1: characterization, gene organization, and chromosomal location. · 2002 · https://pubmed.ncbi.nlm.nih.gov/11827462/ · DOI 10.1006/geno.2001.6678

transport_effect

raises An oocyte transport measurement, which reports the cell interior rising. TAT1's role at the basolateral membrane is efflux, which this record does not measure.

transport_pool

the expressing cell An oocyte transport measurement, which reports the cell interior rising. TAT1's role at the basolateral membrane is efflux, which this record does not measure.

Tryptophan: transport, protein synthesis, neuroactive metabolites, NAD and microbial pathways (2026-09-19) · lines 50–56

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human cloned transporter; expression strongest in kidney and intestine. · source_derived_draft · unverified_draft

## tryptophan-tat1-transport Tryptophan also has an aromatic-amino-acid transport route. Human TAT1 expressed in Xenopus oocytes transported tryptophan, tyrosine, phenylalanine and L-DOPA independently of sodium. Model: Human cloned transporter; expression strongest in kidney and intestine. Limitations: The paper proposes disease relevance; it does not establish TAT1 defects as the cause of blue diaper syndrome. Evidence access: Primary abstract The human T-type amino acid transporter-1: characterization, gene organization, and chromosomal location. · 2002 · https://pubmed.ncbi.nlm.nih.gov/11827462/ · DOI 10.1006/geno.2001.6678

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_access

Primary abstract; primary correction full text reviewed

experimental_model

Human cancer-cell depletion, molecular assays and tumor proteomics.

limitations

Not a DNA mutation or a universal consequence of a low-tryptophan meal. Tumor proteomic filtering was clarified in a correction. Correction record: The 2022 author correction adds omitted funding acknowledgements and clarifies that the maximum-sample peptide filter was used in the intra-tumour analysis (Fig. 3f) but not for W>F substitutants in the tumour-specific analysis (Fig. 3a). Authors report similar biological conclusions with both strategies. This is a publication correction, not an opposing mechanism claim. https://www.nature.com/articles/s41586-022-05097-y

nutrient_topic

Tryptophan collection; molecular form, preparation, species, exposure and manipulation remain explicit. · L-Tryptophan

plain_language

Severe local shortage can change what a cancer cell puts into a protein.

primary_references

Tryptophan depletion results in tryptophan-to-phenylalanine substitutants. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35264796/ · DOI 10.1038/s41586-022-04499-2

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Tryptophan: transport, protein synthesis, neuroactive metabolites, NAD and microbial pathways (2026-09-19) · lines 122–128

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human cancer-cell depletion, molecular assays and tumor proteomics. · source_derived_draft · unverified_draft

## tryptophan-w-to-f-shortage Severe local shortage can change what a cancer cell puts into a protein. Under IFN-gamma/IDO1-associated tryptophan shortage, human cancer cells continued translation with WARS1-associated phenylalanine incorporation at tryptophan positions. Model: Human cancer-cell depletion, molecular assays and tumor proteomics. Limitations: Not a DNA mutation or a universal consequence of a low-tryptophan meal. Tumor proteomic filtering was clarified in a correction. Correction record: The 2022 author correction adds omitted funding acknowledgements and clarifies that the maximum-sample peptide filter was used in the intra-tumour analysis (Fig. 3f) but not for W>F substitutants in the tumour-specific analysis (Fig. 3a). Authors report similar biological conclusions with both strategies. This is a publication correction, not an opposing mechanism claim. https://www.nature.com/articles/s41586-022-05097-y Evidence access: Primary abstract; primary correction full text reviewed Tryptophan depletion results in tryptophan-to-phenylalanine substitutants. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35264796/ · DOI 10.1038/s41586-022-04499-2

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Genomic and phenotypic strain comparisons; convergent loss and laboratory emergence.

limitations

Association is retained as such; this is not direct human host transporter evidence.

nutrient_topic

L-Tyrosine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Tyrosine

plain_language

Microbial access to a nutrient can change its products without stopping growth.

primary_references

Convergent Loss of ABC Transporter Genes From Clostridioides difficile Genomes Is Associated With Impaired Tyrosine Uptake and p-Cresol Production. · 2018 · https://pubmed.ncbi.nlm.nih.gov/29867812/ · DOI 10.3389/fmicb.2018.00901

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Tyrosine: catecholamines, thyroid chemistry, pigment, metabolism and cross-nutrient mechanisms (2026-09-19) · lines 364–370

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Genomic and phenotypic strain comparisons; convergent loss and laboratory emergence. · source_derived_draft · unverified_draft

## l-tyrosine-bacterial-import Microbial access to a nutrient can change its products without stopping growth. Loss of two C. difficile ABC-transporter genes was associated with lower tyrosine/phenylalanine uptake and p-cresol production, without a measurable growth or enterotoxin effect. Model: Genomic and phenotypic strain comparisons; convergent loss and laboratory emergence. Limitations: Association is retained as such; this is not direct human host transporter evidence. Evidence access: Primary abstract Convergent Loss of ABC Transporter Genes From Clostridioides difficile Genomes Is Associated With Impaired Tyrosine Uptake and p-Cresol Production. · 2018 · https://pubmed.ncbi.nlm.nih.gov/29867812/ · DOI 10.3389/fmicb.2018.00901

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Rat amino-acid injection versus control mixture or saline; tissue HPLC.

limitations

Combined depletion is not isolated dietary tyrosine deficiency. Correction record: The 2018 correction (PMID 30094500) reports an error in norepinephrine standard concentrations used for HPLC calibration. The correction abstract was inspected, but full notice content was unavailable; its complete quantitative scope remains unverified. This collection uses the tyrosine depletion and dopamine-transient findings and does not reuse the original norepinephrine concentration result. https://pubmed.ncbi.nlm.nih.gov/30094500/

nutrient_topic

L-Tyrosine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Tyrosine

plain_language

Experimental precursor depletion can reduce local availability.

primary_references

Acute phenylalanine/tyrosine depletion of phasic dopamine in the rat brain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/26944052/ · DOI 10.1007/s00213-016-4259-0

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

L-Tyrosine: catecholamines, thyroid chemistry, pigment, metabolism and cross-nutrient mechanisms (2026-09-19) · lines 380–386

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Rat amino-acid injection versus control mixture or saline; tissue HPLC. · source_derived_draft · unverified_draft

## l-tyrosine-rat-depletion Experimental precursor depletion can reduce local availability. A phenylalanine/tyrosine-free amino-acid injection mixture reduced tyrosine in rat prefrontal cortex and nucleus accumbens. Model: Rat amino-acid injection versus control mixture or saline; tissue HPLC. Limitations: Combined depletion is not isolated dietary tyrosine deficiency. Correction record: The 2018 correction (PMID 30094500) reports an error in norepinephrine standard concentrations used for HPLC calibration. The correction abstract was inspected, but full notice content was unavailable; its complete quantitative scope remains unverified. This collection uses the tyrosine depletion and dopamine-transient findings and does not reuse the original norepinephrine concentration result. https://pubmed.ncbi.nlm.nih.gov/30094500/ Evidence access: Primary abstract Acute phenylalanine/tyrosine depletion of phasic dopamine in the rat brain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/26944052/ · DOI 10.1007/s00213-016-4259-0

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Fast-scan cyclic voltammetry in a separate rat group from the tissue-content experiment.

limitations

The release endpoint is not a direct human measurement; the corrected norepinephrine endpoint is excluded. Correction record: The 2018 correction (PMID 30094500) reports an error in norepinephrine standard concentrations used for HPLC calibration. The correction abstract was inspected, but full notice content was unavailable; its complete quantitative scope remains unverified. This collection uses the tyrosine depletion and dopamine-transient findings and does not reuse the original norepinephrine concentration result. https://pubmed.ncbi.nlm.nih.gov/30094500/

nutrient_topic

L-Tyrosine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Tyrosine

plain_language

Less precursor can change release dynamics without simply emptying all dopamine stores.

primary_references

Acute phenylalanine/tyrosine depletion of phasic dopamine in the rat brain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/26944052/ · DOI 10.1007/s00213-016-4259-0

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

L-Tyrosine: catecholamines, thyroid chemistry, pigment, metabolism and cross-nutrient mechanisms (2026-09-19) · lines 388–394

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Fast-scan cyclic voltammetry in a separate rat group from the tissue-content experiment. · source_derived_draft · unverified_draft

## l-tyrosine-rat-dopamine-transients Less precursor can change release dynamics without simply emptying all dopamine stores. Combined phenylalanine/tyrosine depletion decreased dopamine-transient frequency without decreasing transient amplitude in freely moving rats. Model: Fast-scan cyclic voltammetry in a separate rat group from the tissue-content experiment. Limitations: The release endpoint is not a direct human measurement; the corrected norepinephrine endpoint is excluded. Correction record: The 2018 correction (PMID 30094500) reports an error in norepinephrine standard concentrations used for HPLC calibration. The correction abstract was inspected, but full notice content was unavailable; its complete quantitative scope remains unverified. This collection uses the tyrosine depletion and dopamine-transient findings and does not reuse the original norepinephrine concentration result. https://pubmed.ncbi.nlm.nih.gov/30094500/ Evidence access: Primary abstract Acute phenylalanine/tyrosine depletion of phasic dopamine in the rat brain. · 2016 · https://pubmed.ncbi.nlm.nih.gov/26944052/ · DOI 10.1007/s00213-016-4259-0

evidence_access

Primary abstract

experimental_model

Arterial/renal-vein tracer sampling; comparison with a separate 12-person splanchnic study.

limitations

The organ flux measurement is direct; the assignment to PAH is the established reaction, not selective PAH perturbation in this study.

nutrient_topic

L-Tyrosine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Tyrosine

plain_language

The kidney contributes to precursor production as well as filtration.

primary_references

The kidney is an important site for in vivo phenylalanine-to-tyrosine conversion in adult humans: A metabolic role of the kidney. · 2000 · https://pubmed.ncbi.nlm.nih.gov/10655515/ · DOI 10.1073/pnas.97.3.1242

L-Tyrosine: catecholamines, thyroid chemistry, pigment, metabolism and cross-nutrient mechanisms (2026-09-19) · lines 20–26

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Arterial/renal-vein tracer sampling; comparison with a separate 12-person splanchnic study. · source_derived_draft · unverified_draft

## l-tyrosine-renal-production The kidney contributes to precursor production as well as filtration. Stable-isotope studies in 12 healthy adults demonstrated renal phenylalanine-to-tyrosine conversion and net renal tyrosine release. Model: Arterial/renal-vein tracer sampling; comparison with a separate 12-person splanchnic study. Limitations: The organ flux measurement is direct; the assignment to PAH is the established reaction, not selective PAH perturbation in this study. Evidence access: Primary abstract The kidney is an important site for in vivo phenylalanine-to-tyrosine conversion in adult humans: A metabolic role of the kidney. · 2000 · https://pubmed.ncbi.nlm.nih.gov/10655515/ · DOI 10.1073/pnas.97.3.1242

evidence_access

Primary abstract

experimental_model

Six pigs; isolated loops perfused for 120 minutes with an amino-acid mixture and labeled phenylalanine incorporation.

limitations

An acute local dose response is distinct from chronic whole-diet excess.

nutrient_topic

L-Threonine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Threonine

plain_language

The local amino-acid supply can change how quickly mucus protein is made.

primary_references

Luminal threonine concentration acutely affects intestinal mucosal protein and mucin synthesis in piglets. · 2008 · https://pubmed.ncbi.nlm.nih.gov/18567751/ · DOI 10.1093/jn/138.7.1298

L-Threonine: translation, intestinal barrier, metabolism and cross-nutrient mechanisms (2026-09-19) · lines 210–216

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Six pigs; isolated loops perfused for 120 minutes with an amino-acid mixture and labeled phenylalanine incorporation. · source_derived_draft · unverified_draft

## l-threonine-gut-local-synthesis The local amino-acid supply can change how quickly mucus protein is made. Increasing luminal threonine across 0, 21 and 56 mg/g total amino acids raised measured mucin synthesis in perfused intestinal loops. Model: Six pigs; isolated loops perfused for 120 minutes with an amino-acid mixture and labeled phenylalanine incorporation. Limitations: An acute local dose response is distinct from chronic whole-diet excess. Evidence access: Primary abstract Luminal threonine concentration acutely affects intestinal mucosal protein and mucin synthesis in piglets. · 2008 · https://pubmed.ncbi.nlm.nih.gov/18567751/ · DOI 10.1093/jn/138.7.1298

evidence_access

Primary abstract and PMC full-text Figure 2 and CRISPR methods

experimental_model

Human RT4 cell knockout and 25 mM lactate treatment for 24 hours; Figure 2.

limitations

This is a shared-enzyme connection, not proof that carnosine changes appetite.

nutrient_topic

Carnosine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnosine / beta-alanyl-L-histidine

plain_language

The peptide-processing enzyme also participates in another metabolic pathway.

primary_references

An exercise-inducible metabolite that suppresses feeding and obesity. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35705806/ · DOI 10.1038/s41586-022-04828-5

Carnosine: synthesis, transport, carbonyl chemistry and nutrient interactions (2026-09-19) · lines 172–178

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human RT4 cell knockout and 25 mM lactate treatment for 24 hours; Figure 2. · source_derived_draft · unverified_draft

## carnosine-cndp2-lacphe The peptide-processing enzyme also participates in another metabolic pathway. Deleting CNDP2 in human RT4 bladder epithelial cells reduced Lac-Phe production; extracellular lactate stimulated production in the control cells. Model: Human RT4 cell knockout and 25 mM lactate treatment for 24 hours; Figure 2. Limitations: This is a shared-enzyme connection, not proof that carnosine changes appetite. Evidence access: Primary abstract and PMC full-text Figure 2 and CRISPR methods An exercise-inducible metabolite that suppresses feeding and obesity. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35705806/ · DOI 10.1038/s41586-022-04828-5

evidence_access

Primary abstract

experimental_model

Human intestinal mucosa and red-cell lysate fractionation.

limitations

Intact dipeptide transport was proposed; the cytosolic enzyme was not molecularly identified.

nutrient_topic

Aspartame collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · Aspartame

plain_language

The amino-acid pair can be processed after reaching a different cell compartment.

primary_references

Intestinal hydrolysis of aspartylphenylalanine--the metabolic product of aspartame. · 1986 · https://pubmed.ncbi.nlm.nih.gov/3743970/ · DOI 10.1016/0016-5085(86)90697-9

Aspartame: digestion, taste, metabolite dependencies and experimental signaling (2026-09-20) · lines 26–32

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human intestinal mucosa and red-cell lysate fractionation. · source_derived_draft · unverified_draft

## aspartame-dipeptide-cleavage The amino-acid pair can be processed after reaching a different cell compartment. Brush-border and cytosolic preparations hydrolyzed Asp-Phe; cytosolic fractionation identified one activity peak distinct from seven previously described peptidases. Model: Human intestinal mucosa and red-cell lysate fractionation. Limitations: Intact dipeptide transport was proposed; the cytosolic enzyme was not molecularly identified. Evidence access: Primary abstract Intestinal hydrolysis of aspartylphenylalanine--the metabolic product of aspartame. · 1986 · https://pubmed.ncbi.nlm.nih.gov/3743970/ · DOI 10.1016/0016-5085(86)90697-9

availability_state

biomarker_context Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Balanced Latin-square comparison.

limitations

Acute high-dose kinetics, not brain or safety equivalence.

nutrient_topic

Aspartame collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · Aspartame

plain_language

The same dose need not give the same exposure.

primary_references

Plasma amino acid concentrations in normal adults administered aspartame in capsules or solution: lack of bioequivalence. · 1987 · https://pubmed.ncbi.nlm.nih.gov/3574137/ · DOI 10.1016/0026-0495(87)90052-7

trigger_kind

biomarker_context Imported condition classification; unverified.

Aspartame: digestion, taste, metabolite dependencies and experimental signaling (2026-09-20) · lines 82–88

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Balanced Latin-square comparison. · source_derived_draft · unverified_draft

## aspartame-formulation-phe The same dose need not give the same exposure. In ten adults given 3 g, solution produced an earlier, higher phenylalanine peak than capsules: 191 versus 117 micromol/L at 32 versus 123 minutes. Model: Balanced Latin-square comparison. Limitations: Acute high-dose kinetics, not brain or safety equivalence. Evidence access: Primary abstract Plasma amino acid concentrations in normal adults administered aspartame in capsules or solution: lack of bioequivalence. · 1987 · https://pubmed.ncbi.nlm.nih.gov/3574137/ · DOI 10.1016/0026-0495(87)90052-7

availability_state

biomarker_context Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Same ten-person 3 g comparison.

limitations

The ratio is not a measured change in brain serotonin or dopamine.

nutrient_topic

Aspartame collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · Aspartame

plain_language

Transport competition depends partly on the mixture reaching blood.

primary_references

Plasma amino acid concentrations in normal adults administered aspartame in capsules or solution: lack of bioequivalence. · 1987 · https://pubmed.ncbi.nlm.nih.gov/3574137/ · DOI 10.1016/0026-0495(87)90052-7

trigger_kind

biomarker_context Imported condition classification; unverified.

Aspartame: digestion, taste, metabolite dependencies and experimental signaling (2026-09-20) · lines 90–96

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Same ten-person 3 g comparison. · source_derived_draft · unverified_draft

## aspartame-formulation-ratio Transport competition depends partly on the mixture reaching blood. Solution versus capsules produced a higher plasma phenylalanine-to-other-LNAA ratio, 0.36 versus 0.23. Model: Same ten-person 3 g comparison. Limitations: The ratio is not a measured change in brain serotonin or dopamine. Evidence access: Primary abstract Plasma amino acid concentrations in normal adults administered aspartame in capsules or solution: lack of bioequivalence. · 1987 · https://pubmed.ncbi.nlm.nih.gov/3574137/ · DOI 10.1016/0026-0495(87)90052-7

availability_state

biomarker_context Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Six people per dose; aspartame in orange juice.

limitations

Healthy subjects, not PKU; no direct neurotransmitter assay.

nutrient_topic

Aspartame collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · Aspartame

plain_language

Large loads produce larger amino-acid excursions.

primary_references

Plasma and erythrocyte concentrations of free amino acids in adult humans administered abuse doses of aspartame. · 1981 · https://pubmed.ncbi.nlm.nih.gov/7230277/ · DOI 10.1080/15287398109529980

trigger_kind

biomarker_context Imported condition classification; unverified.

Aspartame: digestion, taste, metabolite dependencies and experimental signaling (2026-09-20) · lines 138–144

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Six people per dose; aspartame in orange juice. · source_derived_draft · unverified_draft

## aspartame-high-dose-phe Large loads produce larger amino-acid excursions. In 18 fasted adults across 100, 150 and 200 mg/kg cohorts, mean plasma phenylalanine peaks were 20.3, 35.1 and 48.7 micromol/dL. Model: Six people per dose; aspartame in orange juice. Limitations: Healthy subjects, not PKU; no direct neurotransmitter assay. Evidence access: Primary abstract Plasma and erythrocyte concentrations of free amino acids in adult humans administered abuse doses of aspartame. · 1981 · https://pubmed.ncbi.nlm.nih.gov/7230277/ · DOI 10.1080/15287398109529980

availability_state

biomarker_context Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Human carrier comparison, also including twelve noncarrier men.

limitations

Heterozygotes do not represent patients with biallelic PAH deficiency; the damaged male-baseline sentence in indexed abstract is not reconstructed.

nutrient_topic

Aspartame collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · Aspartame

plain_language

Reduced metabolic reserve can change the response to a precursor source.

primary_references

Plasma phenylalanine levels in phenylketonuric heterozygous and normal adults administered aspartame at 34 mg/kg body weight. · 1981 · https://pubmed.ncbi.nlm.nih.gov/7268794/ · DOI 10.1016/0300-483x(81)90108-6

trigger_kind

biomarker_context Imported condition classification; unverified.

Aspartame: digestion, taste, metabolite dependencies and experimental signaling (2026-09-20) · lines 146–152

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human carrier comparison, also including twelve noncarrier men. · source_derived_draft · unverified_draft

## aspartame-pku-carrier-kinetics Reduced metabolic reserve can change the response to a precursor source. After 34 mg/kg, twelve female PKU heterozygotes had higher peak phenylalanine than ten noncarrier females, 15.1 versus 8.95 micromol/dL. Model: Human carrier comparison, also including twelve noncarrier men. Limitations: Heterozygotes do not represent patients with biallelic PAH deficiency; the damaged male-baseline sentence in indexed abstract is not reconstructed. Evidence access: Primary abstract Plasma phenylalanine levels in phenylketonuric heterozygous and normal adults administered aspartame at 34 mg/kg body weight. · 1981 · https://pubmed.ncbi.nlm.nih.gov/7268794/ · DOI 10.1016/0300-483x(81)90108-6

availability_state

biomarker_context Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Human beverage crossover; 4.8 g total over eight servings.

limitations

Small healthy-adult study; not a PKU population or a long-term trial.

nutrient_topic

Aspartame collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · Aspartame

plain_language

Repeated exposure did not produce unlimited accumulation in this protocol.

primary_references

Effect of repeated ingestion of aspartame-sweetened beverage on plasma amino acid, blood methanol, and blood formate concentrations in normal adults. · 1989 · https://pubmed.ncbi.nlm.nih.gov/2566887/ · DOI 10.1016/0026-0495(89)90125-x

trigger_kind

biomarker_context Imported condition classification; unverified.

Aspartame: digestion, taste, metabolite dependencies and experimental signaling (2026-09-20) · lines 106–112

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human beverage crossover; 4.8 g total over eight servings. · source_derived_draft · unverified_draft

## aspartame-repeated-phenylalanine Repeated exposure did not produce unlimited accumulation in this protocol. Six adults consumed eight hourly 600 mg servings; phenylalanine rose modestly and plateaued after four to five servings within the reported normal postprandial range. Model: Human beverage crossover; 4.8 g total over eight servings. Limitations: Small healthy-adult study; not a PKU population or a long-term trial. Evidence access: Primary abstract Effect of repeated ingestion of aspartame-sweetened beverage on plasma amino acid, blood methanol, and blood formate concentrations in normal adults. · 1989 · https://pubmed.ncbi.nlm.nih.gov/2566887/ · DOI 10.1016/0026-0495(89)90125-x

evidence_access

Primary full text and author-list correction

experimental_model

Same human crossover.

limitations

Not comparable to isolated cells or susceptible-mouse feeding by dose or endpoint. Correction record: Publisher correction concerns author order, affiliations and citation; no experimental-result correction is stated. Correction PMID 25951455 inspected in full text. https://doi.org/10.1371/journal.pone.0126039

nutrient_topic

Aspartame collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · Aspartame

plain_language

Receptor activity did not translate into a distinct measured response in this meal.

primary_references

Aspartame sensitivity? A double blind randomised crossover study. · 2015 · https://pubmed.ncbi.nlm.nih.gov/25786106/ · DOI 10.1371/journal.pone.0116212

Aspartame: digestion, taste, metabolite dependencies and experimental signaling (2026-09-20) · lines 330–336

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Same human crossover. · source_derived_draft · unverified_draft

## aspartame-snackbar-hormones Receptor activity did not translate into a distinct measured response in this meal. GLP-1, GIP, tyrosine and phenylalanine responses were similar with aspartame and control snack bars. Model: Same human crossover. Limitations: Not comparable to isolated cells or susceptible-mouse feeding by dose or endpoint. Correction record: Publisher correction concerns author order, affiliations and citation; no experimental-result correction is stated. Correction PMID 25951455 inspected in full text. https://doi.org/10.1371/journal.pone.0126039 Evidence access: Primary full text and author-list correction Aspartame sensitivity? A double blind randomised crossover study. · 2015 · https://pubmed.ncbi.nlm.nih.gov/25786106/ · DOI 10.1371/journal.pone.0116212