Component

Human cystathionine beta-synthase / CBS

Human cystathionine beta-synthase / CBS

9 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. PLP-dependent human CBS condenses serine with homocysteine to produce cystathionine.

    Human cystathionine beta-synthase / CBS → Cystathionine source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    Methionine-derived sulfur enters cysteine synthesis.
    experimental_model
    Recombinant truncated human CBS crystallography
    limitations
    Enzyme chemistry alone does not predict whole-body homocysteine during mild deficiency.
    nutrient_topic
    Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B6
    organism
    Homo sapiens
    plain_language
    This B6-dependent step channels homocysteine into transsulfuration.
    primary_references
    [b6-cbs-2001] Structure of human cystathionine beta-synthase: a unique pyridoxal 5'-phosphate-dependent heme protein. (2001). https://pmc.ncbi.nlm.nih.gov/articles/PMC149156/ DOI: 10.1093/emboj/20.15.3910
    tissue_or_cell_type
    Purified recombinant protein; no intact tissue

    Vitamin B6: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 517–527

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Recombinant truncated human CBS crystallography · source_derived_draft · unverified_draft

    ### b6-met-cbs-condensation PLP-dependent human CBS condenses serine with homocysteine to produce cystathionine. Condition category: normal nutrient_topic: Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect. plain_language: This B6-dependent step channels homocysteine into transsulfuration. organism: Homo sapiens tissue_or_cell_type: Purified recombinant protein; no intact tissue experimental_model: Recombinant truncated human CBS crystallography limitations: Enzyme chemistry alone does not predict whole-body homocysteine during mild deficiency. cross_nutrient: Methionine-derived sulfur enters cysteine synthesis. [b6-cbs-2001] Structure of human cystathionine beta-synthase: a unique pyridoxal 5'-phosphate-dependent heme protein. (2001). https://pmc.ncbi.nlm.nih.gov/articles/PMC149156/ DOI: 10.1093/emboj/20.15.3910
    Complete structured claim and evidence

  2. Purified human CBS favored H2S production through replacement of cysteine by homocysteine over the tested alternative cysteine reactions.

    Human cystathionine beta-synthase / CBS → L-Cysteine source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human and yeast CBS kinetics, with human enzyme kept as this record’s subject.
    limitations
    Relative pathway dominance in a tissue cannot be read directly from purified-enzyme substrate tests.
    nutrient_topic
    L-Cysteine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Cysteine
    plain_language
    An enzyme that helps synthesize cysteine can also use it in sulfur-gas production.
    primary_references
    Relative contributions of cystathionine beta-synthase and gamma-cystathionase to H2S biogenesis via alternative trans-sulfuration reactions. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19531479/ · DOI 10.1074/jbc.M109.010868

    L-Cysteine: sulfur allocation, redox supply and cross-nutrient mechanisms (2026-09-19) · lines 284–290

    AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human and yeast CBS kinetics, with human enzyme kept as this record’s subject. · source_derived_draft · unverified_draft

    ## l-cysteine-cbs-h2s-branch An enzyme that helps synthesize cysteine can also use it in sulfur-gas production. Purified human CBS favored H2S production through replacement of cysteine by homocysteine over the tested alternative cysteine reactions. Model: Human and yeast CBS kinetics, with human enzyme kept as this record’s subject. Limitations: Relative pathway dominance in a tissue cannot be read directly from purified-enzyme substrate tests. Evidence access: Primary abstract Relative contributions of cystathionine beta-synthase and gamma-cystathionase to H2S biogenesis via alternative trans-sulfuration reactions. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19531479/ · DOI 10.1074/jbc.M109.010868
    Complete structured claim and evidence

What acts on it

  1. The human CBS structure resolves a heme-binding region distinct from the PLP catalytic site.

    Heme → Human cystathionine beta-synthase / CBS source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    B6 and iron-containing heme meet in one enzyme.
    experimental_model
    Recombinant truncated human CBS crystallography
    limitations
    Heme binding does not establish iron supplementation as a way to increase CBS flux.
    nutrient_topic
    Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B6
    organism
    Homo sapiens
    plain_language
    CBS contains both heme and active vitamin B6.
    primary_references
    [b6-cbs-2001] Structure of human cystathionine beta-synthase: a unique pyridoxal 5'-phosphate-dependent heme protein. (2001). https://pmc.ncbi.nlm.nih.gov/articles/PMC149156/ DOI: 10.1093/emboj/20.15.3910
    tissue_or_cell_type
    Purified recombinant protein; no intact tissue

    Vitamin B6: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 529–539

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Recombinant truncated human CBS crystallography · source_derived_draft · unverified_draft

    ### b6-met-cbs-heme The human CBS structure resolves a heme-binding region distinct from the PLP catalytic site. Condition category: normal nutrient_topic: Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect. plain_language: CBS contains both heme and active vitamin B6. organism: Homo sapiens tissue_or_cell_type: Purified recombinant protein; no intact tissue experimental_model: Recombinant truncated human CBS crystallography limitations: Heme binding does not establish iron supplementation as a way to increase CBS flux. cross_nutrient: B6 and iron-containing heme meet in one enzyme. [b6-cbs-2001] Structure of human cystathionine beta-synthase: a unique pyridoxal 5'-phosphate-dependent heme protein. (2001). https://pmc.ncbi.nlm.nih.gov/articles/PMC149156/ DOI: 10.1093/emboj/20.15.3910
    Complete structured claim and evidence

  2. The human CBS catalytic core binds PLP through its active-site lysine; this site is separate from the heme-binding region.

    PLP → Human cystathionine beta-synthase / CBS source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    Vitamin B6 and sulfur amino-acid metabolism.
    experimental_model
    Recombinant truncated human CBS crystallography
    limitations
    The crystallized human construct lacks the C-terminal regulatory region.
    nutrient_topic
    Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B6
    organism
    Homo sapiens
    plain_language
    CBS uses active vitamin B6 in its catalytic site.
    primary_references
    [b6-cbs-2001] Structure of human cystathionine beta-synthase: a unique pyridoxal 5'-phosphate-dependent heme protein. (2001). https://pmc.ncbi.nlm.nih.gov/articles/PMC149156/ DOI: 10.1093/emboj/20.15.3910
    tissue_or_cell_type
    Purified recombinant protein; no intact tissue

    Vitamin B6: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 505–515

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Recombinant truncated human CBS crystallography · source_derived_draft · unverified_draft

    ### b6-met-cbs-plp The human CBS catalytic core binds PLP through its active-site lysine; this site is separate from the heme-binding region. Condition category: normal nutrient_topic: Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect. plain_language: CBS uses active vitamin B6 in its catalytic site. organism: Homo sapiens tissue_or_cell_type: Purified recombinant protein; no intact tissue experimental_model: Recombinant truncated human CBS crystallography limitations: The crystallized human construct lacks the C-terminal regulatory region. cross_nutrient: Vitamin B6 and sulfur amino-acid metabolism. [b6-cbs-2001] Structure of human cystathionine beta-synthase: a unique pyridoxal 5'-phosphate-dependent heme protein. (2001). https://pmc.ncbi.nlm.nih.gov/articles/PMC149156/ DOI: 10.1093/emboj/20.15.3910
    Complete structured claim and evidence

  3. SAM binding rearranged the human CBS regulatory domain and relieved autoinhibition, improving access to its catalytic pocket.

    S-Adenosyl-L-methionine → Human cystathionine beta-synthase / CBS source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human CBS structural study with SAM-bound activated conformation.
    limitations
    Allosteric regulation does not establish in-vivo flux under every nutritional condition.
    nutrient_topic
    L-Methionine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Methionine
    plain_language
    A plentiful methyl donor can turn up the sulfur-transfer branch.
    primary_references
    Structural insight into the molecular mechanism of allosteric activation of human cystathionine β-synthase by S-adenosylmethionine. · 2014 · https://pubmed.ncbi.nlm.nih.gov/25197074/ · DOI 10.1073/pnas.1414545111

    L-Methionine: transport, methylation, sulfur metabolism and cross-nutrient mechanisms (2026-09-19) · lines 204–210

    AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human CBS structural study with SAM-bound activated conformation. · source_derived_draft · unverified_draft

    ## methionine-cbs-sam-allostery A plentiful methyl donor can turn up the sulfur-transfer branch. SAM binding rearranged the human CBS regulatory domain and relieved autoinhibition, improving access to its catalytic pocket. Model: Human CBS structural study with SAM-bound activated conformation. Limitations: Allosteric regulation does not establish in-vivo flux under every nutritional condition. Evidence access: Primary abstract Structural insight into the molecular mechanism of allosteric activation of human cystathionine β-synthase by S-adenosylmethionine. · 2014 · https://pubmed.ncbi.nlm.nih.gov/25197074/ · DOI 10.1073/pnas.1414545111
    Complete structured claim and evidence

  4. Kinetic simulations predicted that SAM-dependent activation changes the relative CBS contribution to H2S generation at specified substrate concentrations.

    S-Adenosyl-L-methionine → Human cystathionine beta-synthase / CBS source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Simulation based on purified CBS/CSE kinetics with assumed equimolar enzyme concentrations.
    limitations
    A modeled 25–70% contribution is not a directly measured universal human tissue fraction.
    nutrient_topic
    L-Cysteine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Cysteine
    plain_language
    Methylation-cycle chemistry can influence a sulfur-signaling branch.
    primary_references
    Relative contributions of cystathionine beta-synthase and gamma-cystathionase to H2S biogenesis via alternative trans-sulfuration reactions. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19531479/ · DOI 10.1074/jbc.M109.010868

    L-Cysteine: sulfur allocation, redox supply and cross-nutrient mechanisms (2026-09-19) · lines 292–298

    AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Simulation based on purified CBS/CSE kinetics with assumed equimolar enzyme concentrations. · source_derived_draft · unverified_draft

    ## l-cysteine-sam-sulfur-partition Methylation-cycle chemistry can influence a sulfur-signaling branch. Kinetic simulations predicted that SAM-dependent activation changes the relative CBS contribution to H2S generation at specified substrate concentrations. Model: Simulation based on purified CBS/CSE kinetics with assumed equimolar enzyme concentrations. Limitations: A modeled 25–70% contribution is not a directly measured universal human tissue fraction. Evidence access: Primary abstract Relative contributions of cystathionine beta-synthase and gamma-cystathionase to H2S biogenesis via alternative trans-sulfuration reactions. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19531479/ · DOI 10.1074/jbc.M109.010868
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. Tracing in a cultured human hepatoma cell line estimated that transsulfuration supplied homocysteine-derived sulfur to approximately half of the intracellular glutathione pool.

    Homocysteine → GSH source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    B6-dependent transsulfuration connects methionine/homocysteine to the cysteine supply for glutathione.
    experimental_model
    Cultured human hepatoma cell line; metabolic sulfur tracing
    limitations
    Fraction is culture-specific and traces sulfur, not all glutathione atoms; this experiment did not measure dietary B6 depletion.
    nutrient_topic
    Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B6
    organism
    Homo sapiens
    plain_language
    In this cell system, sulfur routed through B6-dependent enzymes helped supply glutathione.
    primary_references
    [b6-glutathione-2000] The quantitatively important relationship between homocysteine metabolism and glutathione synthesis by the transsulfuration pathway and its regulation by redox changes (2000). https://pubmed.ncbi.nlm.nih.gov/11041866/ DOI: 10.1021/bi001088w
    tissue_or_cell_type
    Cultured human hepatoma cell line

    Vitamin B6: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 590–600

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Cultured human hepatoma cell line; metabolic sulfur tracing · source_derived_draft · unverified_draft

    ### b6-met-transsulfuration-glutathione Tracing in a cultured human hepatoma cell line estimated that transsulfuration supplied homocysteine-derived sulfur to approximately half of the intracellular glutathione pool. Condition category: normal nutrient_topic: Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect. plain_language: In this cell system, sulfur routed through B6-dependent enzymes helped supply glutathione. organism: Homo sapiens tissue_or_cell_type: Cultured human hepatoma cell line experimental_model: Cultured human hepatoma cell line; metabolic sulfur tracing limitations: Fraction is culture-specific and traces sulfur, not all glutathione atoms; this experiment did not measure dietary B6 depletion. cross_nutrient: B6-dependent transsulfuration connects methionine/homocysteine to the cysteine supply for glutathione. [b6-glutathione-2000] The quantitatively important relationship between homocysteine metabolism and glutathione synthesis by the transsulfuration pathway and its regulation by redox changes (2000). https://pubmed.ncbi.nlm.nih.gov/11041866/ DOI: 10.1021/bi001088w
    Complete structured claim and evidence

  2. TXNDC17 knockout shifted human-cell cysteine supply toward transsulfuration, as assessed using labeled methionine and downstream sulfur metabolites.

    Human TXNDC17 loss → Human-cell cysteine supply through transsulfuration source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    evidence_access
    Primary full text
    experimental_model
    Human HEK293 metabolic tracing and enzyme perturbation.
    limitations
    Compensation requires intact transsulfuration and does not prove that B6 supplementation rescues every transport defect.
    nutrient_topic
    L-Cysteine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Cysteine
    plain_language
    An internal synthesis route compensated when imported cystine was harder to use.
    primary_references
    TRP14 is the rate-limiting enzyme for intracellular cystine reduction and regulates proteome cysteinylation. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38811853/ · DOI 10.1038/s44318-024-00117-1
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    L-Cysteine: sulfur allocation, redox supply and cross-nutrient mechanisms (2026-09-19) · lines 76–82

    AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human HEK293 metabolic tracing and enzyme perturbation. · source_derived_draft · unverified_draft

    ## l-cysteine-trp14-compensation An internal synthesis route compensated when imported cystine was harder to use. TXNDC17 knockout shifted human-cell cysteine supply toward transsulfuration, as assessed using labeled methionine and downstream sulfur metabolites. Model: Human HEK293 metabolic tracing and enzyme perturbation. Limitations: Compensation requires intact transsulfuration and does not prove that B6 supplementation rescues every transport defect. Evidence access: Primary full text TRP14 is the rate-limiting enzyme for intracellular cystine reduction and regulates proteome cysteinylation. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38811853/ · DOI 10.1038/s44318-024-00117-1
    Complete structured claim and evidence

  3. The study reported opposite CTH and CBS expression responses between the two breast cancer cell lines.

    S-allyl-L-cysteine / SAC → Cell-line-dependent CTH/CBS expression response to SAC source_derived_draftungraded
    Experimental context and source evidence
    acting_entity
    s-allylcysteine
    dose
    2.24, 3.37 or 4.50 mM SAC
    duration
    2, 4, 6, 8 or 24 hours
    evidence_access
    Primary abstract
    experimental_comparison
    SAC versus untreated cell controls
    experimental_model
    MCF-7 and MDA-MB-231 breast adenocarcinoma cells
    interpretation_status
    Source-derived research curation; not independent primary verification
    limitations
    Abstract does not resolve every time/dose direction; these must be retrieved before assigning a universal signed enzyme edge.
    nutrient_topic
    S-allylcysteine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · S-allyl-L-cysteine / SAC
    organism
    Homo sapiens
    plain_language
    The cellular background changed the direction of the response.
    primary_references
    [38397425] S-Allyl-L-Cysteine Affects Cell Proliferation and Expression of H2S-Synthetizing Enzymes in MCF-7 and MDA-MB-231 Adenocarcinoma Cell Lines. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38397425/ · DOI 10.3390/biom14020188
    route
    Cell culture
    tissue_or_cell_type
    MCF-7 and MDA-MB-231 breast adenocarcinoma cells

    S-allylcysteine: sulfur signaling, redox responses and cross-nutrient mechanisms (2026-09-20) · lines 302–309

    AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · MCF-7 and MDA-MB-231 breast adenocarcinoma cells · source_derived_draft · unverified_draft

    ## s-allylcysteine-breast-cth-cbs-context The cellular background changed the direction of the response. The study reported opposite CTH and CBS expression responses between the two breast cancer cell lines. Model: MCF-7 and MDA-MB-231 breast adenocarcinoma cells Limitations: Abstract does not resolve every time/dose direction; these must be retrieved before assigning a universal signed enzyme edge. Evidence access: Primary abstract [38397425] S-Allyl-L-Cysteine Affects Cell Proliferation and Expression of H2S-Synthetizing Enzymes in MCF-7 and MDA-MB-231 Adenocarcinoma Cell Lines. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38397425/ · DOI 10.3390/biom14020188 Structured context: {"organism": "Homo sapiens", "tissue_or_cell_type": "MCF-7 and MDA-MB-231 breast adenocarcinoma cells", "dose": "2.24, 3.37 or 4.50 mM SAC", "duration": "2, 4, 6, 8 or 24 hours", "route": "Cell culture", "experimental_comparison": "SAC versus untreated cell controls", "acting_entity": "s-allylcysteine", "interpretation_status": "Source-derived research curation; not independent primary verification"}
    Complete structured claim and evidence

In the sources

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

    This is a research prototype built from draft material. It is not medical advice, and its statements still await verification against the original studies.

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