Component

Human carnitine transporter OCTN2 / SLC22A5

Human carnitine transporter OCTN2 / SLC22A5. Species, exposure and limitations are retained in each linked claim.

10 recorded relationships. Experimental role, claim status and evidence remain attached to each record.

Read recorded mechanisms Open recursive mind map

How nutrients influence it

Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.

How nutrients reach it in more than one step

Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.

Tracing routes…

What it does

Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.

Recorded relationships

What it acts on

  1. Human OCTN2 expression increased sodium-dependent carnitine uptake with an apparent Km of 4.34 micromolar.

    Human carnitine transporter OCTN2 / SLC22A5 → L-Carnitine source_derived_draftungraded
    Experimental context and source evidence
    evidence_span
    {"source_cache": "artifacts/sodium-research/9685390.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "08cdedaad32299795a52b81183d565d2b476b7a190b2af7b950c829f8c11ddf6", "start_char": 0, "end_char": 1549, "text_sha256": "08cdedaad32299795a52b81183d565d2b476b7a190b2af7b950c829f8c11ddf6"}
    experimental_model
    Cloning and functional expression
    exposure
    Radiolabeled carnitine uptake and sodium dependence
    limitations
    Expression assay; dietary sodium intake, mitochondrial fatty-acid oxidation and clinical supplementation were not directly tested.
    nutrient_topic
    Sodium research collection; topical membership is not evidence of a direct dietary effect. · Sodium
    organism
    Human OCTN2 in HEK293 cells
    plain_language
    The sodium gradient helps bring carnitine into cells.
    primary_references
    [sodium-p9685390] Molecular and functional identification of sodium ion-dependent, high affinity human carnitine transporter OCTN2. (1998). https://pubmed.ncbi.nlm.nih.gov/9685390/ DOI: 10.1074/jbc.273.32.20378
    tissue_or_cell_type
    Cell plasma membrane
    transport_effect
    raises Expression increased sodium-dependent carnitine uptake.
    transport_pool
    the expressing cell Expression increased sodium-dependent carnitine uptake.

    Sodium: gradients, nutrient transport, fluid regulation and loss states (2026-09-17) · lines 616–627

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Cloning and functional expression · source_derived_draft · unverified_draft

    ### sodium-octn2-carnitine Human OCTN2 expression increased sodium-dependent carnitine uptake with an apparent Km of 4.34 micromolar. Condition category: normal nutrient_topic: Sodium research collection; topical membership is not evidence of a direct dietary effect. plain_language: The sodium gradient helps bring carnitine into cells. organism: Human OCTN2 in HEK293 cells tissue_or_cell_type: Cell plasma membrane experimental_model: Cloning and functional expression limitations: Expression assay; dietary sodium intake, mitochondrial fatty-acid oxidation and clinical supplementation were not directly tested. exposure: Radiolabeled carnitine uptake and sodium dependence evidence_span: {"source_cache": "artifacts/sodium-research/9685390.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "08cdedaad32299795a52b81183d565d2b476b7a190b2af7b950c829f8c11ddf6", "start_char": 0, "end_char": 1549, "text_sha256": "08cdedaad32299795a52b81183d565d2b476b7a190b2af7b950c829f8c11ddf6"} [sodium-p9685390] Molecular and functional identification of sodium ion-dependent, high affinity human carnitine transporter OCTN2. (1998). https://pubmed.ncbi.nlm.nih.gov/9685390/ DOI: 10.1074/jbc.273.32.20378
    Complete structured claim and evidence

  2. Wild-type human SLC22A5 did not transport ergothioneine in the comparative expression assay.

    Human carnitine transporter OCTN2 / SLC22A5 → L-Ergothioneine source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human wild-type transporters expressed in HEK293 cells.
    limitations
    Related sequence does not establish substrate interchangeability.
    nutrient_topic
    Ergothioneine collection; molecular form, preparation, species, exposure and manipulation remain explicit. · L-Ergothioneine
    plain_language
    The main carnitine carrier cannot be assumed to carry ergothioneine.
    primary_references
    Substrate discrimination by ergothioneine transporter SLC22A4 and carnitine transporter SLC22A5: gain-of-function by interchange of selected amino acids. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19814996/ · DOI 10.1016/j.bbamem.2009.09.019

    Ergothioneine: transport, redox chemistry and cross-nutrient mechanisms (2026-09-19) · lines 40–46

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

    ## ergothioneine-slc22a5-not-ergo The main carnitine carrier cannot be assumed to carry ergothioneine. Wild-type human SLC22A5 did not transport ergothioneine in the comparative expression assay. Model: Human wild-type transporters expressed in HEK293 cells. Limitations: Related sequence does not establish substrate interchangeability. Evidence access: Primary abstract Substrate discrimination by ergothioneine transporter SLC22A4 and carnitine transporter SLC22A5: gain-of-function by interchange of selected amino acids. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19814996/ · DOI 10.1016/j.bbamem.2009.09.019
    Complete structured claim and evidence

  3. Expressed human OCTN2 transported acetyl-L-carnitine in a sodium-dependent manner with a measured Km of 8.5 micromolar.

    Human carnitine transporter OCTN2 / SLC22A5 → Acetyl-L-carnitine source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human OCTN2 in HEK293 cells.
    limitations
    A kinetic constant is not a treatment target.
    nutrient_topic
    L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine
    plain_language
    The transporter also carries the acetylated form.
    primary_references
    Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/
    transport_effect
    raises Sodium-dependent acetylcarnitine transport with a measured Km of 8.5 micromolar.
    transport_pool
    the expressing cell Sodium-dependent acetylcarnitine transport with a measured Km of 8.5 micromolar.

    L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 50–56

    AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human OCTN2 in HEK293 cells. · source_derived_draft · unverified_draft

    ## l-carnitine-octn2-acetyl The transporter also carries the acetylated form. Expressed human OCTN2 transported acetyl-L-carnitine in a sodium-dependent manner with a measured Km of 8.5 micromolar. Model: Human OCTN2 in HEK293 cells. Limitations: A kinetic constant is not a treatment target. Evidence access: Primary abstract Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/
    Complete structured claim and evidence

  4. Fibroblasts carrying truncating OCTN2 variants from two unrelated patients lacked mediated carnitine transport.

    Human carnitine transporter OCTN2 / SLC22A5 → Human OCTN2-mediated cellular carnitine transport source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    evidence_access
    Primary abstract
    experimental_model
    Human primary-carnitine-deficiency patient fibroblasts and variant expression.
    limitations
    Genetic transport failure differs from low dietary intake.
    nutrient_topic
    L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine
    plain_language
    A broken cell-entry mechanism can produce primary carnitine deficiency.
    primary_references
    Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10051646/ · DOI 10.1073/pnas.96.5.2356
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 66–72

    AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human primary-carnitine-deficiency patient fibroblasts and variant expression. · source_derived_draft · unverified_draft

    ## l-carnitine-octn2-loss A broken cell-entry mechanism can produce primary carnitine deficiency. Fibroblasts carrying truncating OCTN2 variants from two unrelated patients lacked mediated carnitine transport. Model: Human primary-carnitine-deficiency patient fibroblasts and variant expression. Limitations: Genetic transport failure differs from low dietary intake. Evidence access: Primary abstract Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10051646/ · DOI 10.1073/pnas.96.5.2356
    Complete structured claim and evidence

  5. Transfecting patient fibroblasts with normal OCTN2 cDNA partially restored carnitine transport.

    Human carnitine transporter OCTN2 / SLC22A5 → Human OCTN2-mediated cellular carnitine transport source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    evidence_access
    Primary abstract
    experimental_model
    Patient fibroblast gene-complementation experiment.
    limitations
    This is experimental gene complementation, not a clinical gene-therapy result.
    nutrient_topic
    L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine
    plain_language
    Replacing the missing transport function rescued uptake in cells.
    primary_references
    Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10051646/ · DOI 10.1073/pnas.96.5.2356
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 74–80

    AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Patient fibroblast gene-complementation experiment. · source_derived_draft · unverified_draft

    ## l-carnitine-octn2-rescue Replacing the missing transport function rescued uptake in cells. Transfecting patient fibroblasts with normal OCTN2 cDNA partially restored carnitine transport. Model: Patient fibroblast gene-complementation experiment. Limitations: This is experimental gene complementation, not a clinical gene-therapy result. Evidence access: Primary abstract Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10051646/ · DOI 10.1073/pnas.96.5.2356
    Complete structured claim and evidence

  6. Human OCTN2 transport measurements were consistent with approximately one sodium ion accompanying each carnitine molecule.

    Human carnitine transporter OCTN2 / SLC22A5 → L-Carnitine source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human OCTN2 expressed in HEK293 cells.
    limitations
    Does not imply that eating more salt improves carnitine uptake.
    nutrient_topic
    L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine
    plain_language
    Cell entry depends on a sodium-coupled transporter.
    primary_references
    Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/
    transport_effect
    raises Sodium-coupled, with about one sodium ion accompanying each carnitine molecule inward.
    transport_pool
    the expressing cell Sodium-coupled, with about one sodium ion accompanying each carnitine molecule inward.

    L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 42–48

    AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human OCTN2 expressed in HEK293 cells. · source_derived_draft · unverified_draft

    ## l-carnitine-octn2-sodium Cell entry depends on a sodium-coupled transporter. Human OCTN2 transport measurements were consistent with approximately one sodium ion accompanying each carnitine molecule. Model: Human OCTN2 expressed in HEK293 cells. Limitations: Does not imply that eating more salt improves carnitine uptake. Evidence access: Primary abstract Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. Human OCTN2 transported D-carnitine with lower affinity than L-carnitine: reported Km values were 10.9 versus 4.3 micromolar.

    D-Carnitine → L-Carnitine source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Transporter expression assay.
    limitations
    D-carnitine is an experimental comparator, not a substitute.
    nutrient_topic
    L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine
    plain_language
    The two mirror-image molecules are handled differently.
    primary_references
    Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/

    L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 58–64

    AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Transporter expression assay. · source_derived_draft · unverified_draft

    ## l-carnitine-octn2-stereo The two mirror-image molecules are handled differently. Human OCTN2 transported D-carnitine with lower affinity than L-carnitine: reported Km values were 10.9 versus 4.3 micromolar. Model: Transporter expression assay. Limitations: D-carnitine is an experimental comparator, not a substitute. Evidence access: Primary abstract Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/
    Complete structured claim and evidence

  2. Human OCTN2 cryo-EM structures identified a sodium-binding cavity separate from the carnitine site, with allosteric coupling supported by electrophysiology.

    Sodium ion → Human OCTN2 allosteric sodium-binding site source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human OCTN2 structures in ligand-free, carnitine/sodium-bound and ipratropium-bound conformations; 2025 primary study.
    limitations
    Structural coupling does not show that more sodium intake increases transport.
    nutrient_topic
    L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine
    plain_language
    Sodium supports transport through a separate coupled binding site.
    primary_references
    Structural basis of sodium ion-dependent carnitine transport by OCTN2. · 2025 · https://pubmed.ncbi.nlm.nih.gov/41318751/ · DOI 10.1038/s41467-025-66867-6

    L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 490–496

    AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human OCTN2 structures in ligand-free, carnitine/sodium-bound and ipratropium-bound conformations; 2025 primary study. · source_derived_draft · unverified_draft

    ## l-carnitine-octn2-structure Sodium supports transport through a separate coupled binding site. Human OCTN2 cryo-EM structures identified a sodium-binding cavity separate from the carnitine site, with allosteric coupling supported by electrophysiology. Model: Human OCTN2 structures in ligand-free, carnitine/sodium-bound and ipratropium-bound conformations; 2025 primary study. Limitations: Structural coupling does not show that more sodium intake increases transport. Evidence access: Primary abstract Structural basis of sodium ion-dependent carnitine transport by OCTN2. · 2025 · https://pubmed.ncbi.nlm.nih.gov/41318751/ · DOI 10.1038/s41467-025-66867-6
    Complete structured claim and evidence

  3. In a reported patient with homozygous SLC22A5-associated primary carnitine deficiency and a cardiac presentation, cardiac function remained normal during 14 years of oral carnitine treatment.

    L-Carnitine → Human cardiac function in primary carnitine deficiency source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    evidence_access
    Primary abstract
    experimental_model
    Single human case and long-term follow-up.
    limitations
    One case, no untreated comparator; not proof of general cardiovascular benefit.
    nutrient_topic
    L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine
    plain_language
    Treating a confirmed transport disorder can have a different role from general supplementation.
    primary_references
    Primary systemic carnitine deficiency: a Turkish case with a novel homozygous SLC22A5 mutation and 14 years follow-up. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26030785/ · DOI 10.1515/jpem-2014-0528
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 82–88

    AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Single human case and long-term follow-up. · source_derived_draft · unverified_draft

    ## l-carnitine-primary-heart Treating a confirmed transport disorder can have a different role from general supplementation. In a reported patient with homozygous SLC22A5-associated primary carnitine deficiency and a cardiac presentation, cardiac function remained normal during 14 years of oral carnitine treatment. Model: Single human case and long-term follow-up. Limitations: One case, no untreated comparator; not proof of general cardiovascular benefit. Evidence access: Primary abstract Primary systemic carnitine deficiency: a Turkish case with a novel homozygous SLC22A5 mutation and 14 years follow-up. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26030785/ · DOI 10.1515/jpem-2014-0528
    Complete structured claim and evidence

  4. Valproylcarnitine fractional renal excretion approached 100%, unlike the strongly reabsorbed free carnitine pool; transporter assays showed low OCTN2 affinity.

    Valproyl-L-carnitine → Human renal fractional excretion of valproylcarnitine source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human urine/plasma measurements and OCTN2 assays.
    limitations
    The authors found that excreted valproylcarnitine did not impair renal handling of free carnitine in vivo.
    nutrient_topic
    L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine
    plain_language
    The drug-linked ester is handled differently from free carnitine.
    primary_references
    Effect of short- and long-term treatment with valproate on carnitine homeostasis in humans. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22743351/ · DOI 10.1097/FTD.0b013e3182608e2f

    L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 290–296

    AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human urine/plasma measurements and OCTN2 assays. · source_derived_draft · unverified_draft

    ## l-carnitine-valproate-clearance The drug-linked ester is handled differently from free carnitine. Valproylcarnitine fractional renal excretion approached 100%, unlike the strongly reabsorbed free carnitine pool; transporter assays showed low OCTN2 affinity. Model: Human urine/plasma measurements and OCTN2 assays. Limitations: The authors found that excreted valproylcarnitine did not impair renal handling of free carnitine in vivo. Evidence access: Primary abstract Effect of short- and long-term treatment with valproate on carnitine homeostasis in humans. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22743351/ · DOI 10.1097/FTD.0b013e3182608e2f
    Complete structured claim and evidence

In the sources

Preserved passages that mention this component, quoted exactly. Open one to read it in context.

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