Component

Human MMACHC / cobalamin-processing protein CblC

Human MMACHC / cobalamin-processing protein CblC

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. Purified human CblC/MMACHC supported GSH-dependent decyanation of cyanocobalamin to cob(II)alamin efficiently under anaerobic conditions; the human reaction was oxygen-sensitive.

    Human MMACHC / cobalamin-processing protein CblC → Cyanocobalamin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Abstract; indexed primary Results summary
    experimental_model
    Purified human MMACHC; oxygen-controlled biochemical assay
    exposure
    GSH and specified B12 form under anaerobic versus aerobic conditions
    limitations
    Abstract-level extraction; stronger aerobic activity of the C. elegans enzyme must not be attributed to human MMACHC.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Glutathione could supply reducing power, but oxygen strongly affected this human-protein reaction.
    primary_references
    [li-2014-gsh-electron] Glutathione-dependent one-electron transfer reactions catalyzed by a B12 trafficking protein (2014). https://pubmed.ncbi.nlm.nih.gov/24742678/ DOI: 10.1074/jbc.M114.567339
    tissue_or_cell_type
    Cell-free assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 767–779

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human MMACHC; oxygen-controlled biochemical assay · source_derived_draft · unverified_draft

    ### b12-human-gsh-decyanation Purified human CblC/MMACHC supported GSH-dependent decyanation of cyanocobalamin to cob(II)alamin efficiently under anaerobic conditions; the human reaction was oxygen-sensitive. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Glutathione could supply reducing power, but oxygen strongly affected this human-protein reaction. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Purified human MMACHC; oxygen-controlled biochemical assay limitations: Abstract-level extraction; stronger aerobic activity of the C. elegans enzyme must not be attributed to human MMACHC. exposure: GSH and specified B12 form under anaerobic versus aerobic conditions cross_nutrient: true evidence_location: Abstract; indexed primary Results summary [li-2014-gsh-electron] Glutathione-dependent one-electron transfer reactions catalyzed by a B12 trafficking protein (2014). https://pubmed.ncbi.nlm.nih.gov/24742678/ DOI: 10.1074/jbc.M114.567339
    Complete structured claim and evidence

  2. Purified human CblC/MMACHC supported GSH-dependent reduction of aquocobalamin to cob(II)alamin efficiently under anaerobic conditions; the human reaction was oxygen-sensitive.

    Human MMACHC / cobalamin-processing protein CblC → Aquocobalamin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Abstract; indexed primary Results summary
    experimental_model
    Purified human MMACHC; oxygen-controlled biochemical assay
    exposure
    GSH and specified B12 form under anaerobic versus aerobic conditions
    limitations
    Abstract-level extraction; stronger aerobic activity of the C. elegans enzyme must not be attributed to human MMACHC.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Glutathione could supply reducing power, but oxygen strongly affected this human-protein reaction.
    primary_references
    [li-2014-gsh-electron] Glutathione-dependent one-electron transfer reactions catalyzed by a B12 trafficking protein (2014). https://pubmed.ncbi.nlm.nih.gov/24742678/ DOI: 10.1074/jbc.M114.567339
    tissue_or_cell_type
    Cell-free assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 781–793

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human MMACHC; oxygen-controlled biochemical assay · source_derived_draft · unverified_draft

    ### b12-human-gsh-reduction Purified human CblC/MMACHC supported GSH-dependent reduction of aquocobalamin to cob(II)alamin efficiently under anaerobic conditions; the human reaction was oxygen-sensitive. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Glutathione could supply reducing power, but oxygen strongly affected this human-protein reaction. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Purified human MMACHC; oxygen-controlled biochemical assay limitations: Abstract-level extraction; stronger aerobic activity of the C. elegans enzyme must not be attributed to human MMACHC. exposure: GSH and specified B12 form under anaerobic versus aerobic conditions cross_nutrient: true evidence_location: Abstract; indexed primary Results summary [li-2014-gsh-electron] Glutathione-dependent one-electron transfer reactions catalyzed by a B12 trafficking protein (2014). https://pubmed.ncbi.nlm.nih.gov/24742678/ DOI: 10.1074/jbc.M114.567339
    Complete structured claim and evidence

  3. Human MMACHC transfers the 5′-deoxyadenosyl group from adenosylcobalamin to glutathione, yielding cob(I)alamin and the corresponding glutathione thioether; reported turnover was 0.174 +/- 0.006 per hour at 20 C.

    Human MMACHC / cobalamin-processing protein CblC → 5'-Deoxyadenosylcobalamin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Primary abstract; indexed article Introduction/Figure 1
    experimental_model
    Purified human MMACHC substrate chemistry
    exposure
    Specified alkylcobalamin plus GSH; kinetic temperature 20 C
    limitations
    Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Glutathione receives the side group removed from this B12 form.
    primary_references
    [kim-2009-gsh-dealkylation] A human vitamin B12 trafficking protein uses glutathione transferase activity for processing alkylcobalamins (2009). https://pubmed.ncbi.nlm.nih.gov/19801555/ DOI: 10.1074/jbc.M109.057877
    tissue_or_cell_type
    Cell-free assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 725–737

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human MMACHC substrate chemistry · source_derived_draft · unverified_draft

    ### b12-mmachc-adenosyl-dealkylation Human MMACHC transfers the 5′-deoxyadenosyl group from adenosylcobalamin to glutathione, yielding cob(I)alamin and the corresponding glutathione thioether; reported turnover was 0.174 +/- 0.006 per hour at 20 C. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Glutathione receives the side group removed from this B12 form. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Purified human MMACHC substrate chemistry limitations: Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans. exposure: Specified alkylcobalamin plus GSH; kinetic temperature 20 C cross_nutrient: true evidence_location: Primary abstract; indexed article Introduction/Figure 1 [kim-2009-gsh-dealkylation] A human vitamin B12 trafficking protein uses glutathione transferase activity for processing alkylcobalamins (2009). https://pubmed.ncbi.nlm.nih.gov/19801555/ DOI: 10.1074/jbc.M109.057877
    Complete structured claim and evidence

  4. Human MMACHC converted bound cyanocobalamin to cob(II)alamin during NADPH-supported reductive decyanation; EPR identified the product in a base-off coordination state.

    Human MMACHC / cobalamin-processing protein CblC → Cyanocobalamin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Results: Figure 4; Materials and Methods: Decyanation of CNCbl
    experimental_model
    Purified human MMACHC with human flavoprotein donor
    exposure
    Anaerobic CNCbl/MMACHC, NADPH and MTRR or NDOR1
    limitations
    Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Processing removes the cyano group and leaves a reduced B12 intermediate.
    primary_references
    [kim-2008-decyanation] Decyanation of vitamin B12 by a trafficking chaperone (2008). https://pubmed.ncbi.nlm.nih.gov/18779575/ DOI: 10.1073/pnas.0805989105
    tissue_or_cell_type
    Cell-free assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 669–681

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human MMACHC with human flavoprotein donor · source_derived_draft · unverified_draft

    ### b12-mmachc-decyanation Human MMACHC converted bound cyanocobalamin to cob(II)alamin during NADPH-supported reductive decyanation; EPR identified the product in a base-off coordination state. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Processing removes the cyano group and leaves a reduced B12 intermediate. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Purified human MMACHC with human flavoprotein donor limitations: Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans. exposure: Anaerobic CNCbl/MMACHC, NADPH and MTRR or NDOR1 cross_nutrient: true evidence_location: Results: Figure 4; Materials and Methods: Decyanation of CNCbl [kim-2008-decyanation] Decyanation of vitamin B12 by a trafficking chaperone (2008). https://pubmed.ncbi.nlm.nih.gov/18779575/ DOI: 10.1073/pnas.0805989105
    Complete structured claim and evidence

  5. Human MMACHC transfers the methyl group from methylcobalamin to glutathione, yielding cob(I)alamin and the corresponding glutathione thioether; reported turnover was 11.7 +/- 0.2 per hour at 20 C.

    Human MMACHC / cobalamin-processing protein CblC → Methylcobalamin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Primary abstract; indexed article Introduction/Figure 1
    experimental_model
    Purified human MMACHC substrate chemistry
    exposure
    Specified alkylcobalamin plus GSH; kinetic temperature 20 C
    limitations
    Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Glutathione receives the side group removed from this B12 form.
    primary_references
    [kim-2009-gsh-dealkylation] A human vitamin B12 trafficking protein uses glutathione transferase activity for processing alkylcobalamins (2009). https://pubmed.ncbi.nlm.nih.gov/19801555/ DOI: 10.1074/jbc.M109.057877
    tissue_or_cell_type
    Cell-free assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 711–723

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human MMACHC substrate chemistry · source_derived_draft · unverified_draft

    ### b12-mmachc-methyl-dealkylation Human MMACHC transfers the methyl group from methylcobalamin to glutathione, yielding cob(I)alamin and the corresponding glutathione thioether; reported turnover was 11.7 +/- 0.2 per hour at 20 C. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Glutathione receives the side group removed from this B12 form. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Purified human MMACHC substrate chemistry limitations: Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans. exposure: Specified alkylcobalamin plus GSH; kinetic temperature 20 C cross_nutrient: true evidence_location: Primary abstract; indexed article Introduction/Figure 1 [kim-2009-gsh-dealkylation] A human vitamin B12 trafficking protein uses glutathione transferase activity for processing alkylcobalamins (2009). https://pubmed.ncbi.nlm.nih.gov/19801555/ DOI: 10.1074/jbc.M109.057877
    Complete structured claim and evidence

What acts on it

  1. Human MMADHC donated the Cys261 sulfur ligand to MMACHC-bound cob(II)alamin, forming an interprotein complex that oxidized to thiolato-cob(III)alamin.

    Human MMADHC / cobalamin-trafficking protein CblD → Human MMACHC / cobalamin-processing protein CblC source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Abstract; indexed Results: CblD binds H2OCbl and forms a complex with CblC
    experimental_model
    Human recombinant chaperones; cysteine scanning and EPR/X-ray absorption
    exposure
    MMACHC-bound cob(II)alamin mixed with MMADHC; oxygen controls
    limitations
    Chemical complex formation does not alone prove the complete in-cell route from lysosome to either client enzyme.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    A sulfur atom on one chaperone helped hold B12 while it remained bound to the other.
    primary_references
    [li-2020-co-s] An Interprotein Co-S Coordination Complex in the B12-Trafficking Pathway (2020). https://pubmed.ncbi.nlm.nih.gov/32871076/ DOI: 10.1021/jacs.0c06590
    tissue_or_cell_type
    Cell-free assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 879–891

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human recombinant chaperones; cysteine scanning and EPR/X-ray absorption · source_derived_draft · unverified_draft

    ### b12-mmad-cys261-co-s Human MMADHC donated the Cys261 sulfur ligand to MMACHC-bound cob(II)alamin, forming an interprotein complex that oxidized to thiolato-cob(III)alamin. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: A sulfur atom on one chaperone helped hold B12 while it remained bound to the other. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Human recombinant chaperones; cysteine scanning and EPR/X-ray absorption limitations: Chemical complex formation does not alone prove the complete in-cell route from lysosome to either client enzyme. exposure: MMACHC-bound cob(II)alamin mixed with MMADHC; oxygen controls cross_nutrient: false evidence_location: Abstract; indexed Results: CblD binds H2OCbl and forms a complex with CblC [li-2020-co-s] An Interprotein Co-S Coordination Complex in the B12-Trafficking Pathway (2020). https://pubmed.ncbi.nlm.nih.gov/32871076/ DOI: 10.1021/jacs.0c06590
    Complete structured claim and evidence

  2. Human MMADHC delta123 carrying T182N showed strongly reduced complex formation with full-length human MMACHC after MeCbl/GSH incubation, compared with matched delta123 MMADHC.

    Human MMADHC delta123 T182N → Human MMACHC / cobalamin-processing protein CblC source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    cross_nutrient
    false
    evidence_location
    Results: Figure 5D; Experimental Procedures
    experimental_model
    Recombinant human proteins; blue-native PAGE
    exposure
    T182N versus matched delta123 comparator, MMACHC, MeCbl and GSH
    limitations
    Functional assay used human proteins; mouse MMADHC was used for the separate crystal structure. Truncation may affect full-length behavior.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    This variant disrupted the two processing proteins’ association.
    primary_references
    [froese-2015-complex] Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B12 Trafficking (2015). https://pubmed.ncbi.nlm.nih.gov/26483544/ DOI: 10.1074/jbc.M115.683268
    tissue_or_cell_type
    Cell-free assay
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 865–877

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Recombinant human proteins; blue-native PAGE · source_derived_draft · unverified_draft

    ### b12-mmad-t182n-complex Human MMADHC delta123 carrying T182N showed strongly reduced complex formation with full-length human MMACHC after MeCbl/GSH incubation, compared with matched delta123 MMADHC. Condition category: machinery_impairment nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: This variant disrupted the two processing proteins’ association. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Recombinant human proteins; blue-native PAGE limitations: Functional assay used human proteins; mouse MMADHC was used for the separate crystal structure. Truncation may affect full-length behavior. exposure: T182N versus matched delta123 comparator, MMACHC, MeCbl and GSH cross_nutrient: false evidence_location: Results: Figure 5D; Experimental Procedures [froese-2015-complex] Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B12 Trafficking (2015). https://pubmed.ncbi.nlm.nih.gov/26483544/ DOI: 10.1074/jbc.M115.683268
    Complete structured claim and evidence

  3. Recombinant human MTRR with NADPH supported MMACHC-bound cyanocobalamin conversion to cob(II)alamin; free cyanocobalamin was not detectably reduced without MMACHC.

    Methionine synthase reductase / MTRR → Human MMACHC / cobalamin-processing protein CblC source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Results: Figure 4; Materials and Methods: Decyanation of CNCbl
    experimental_model
    Human purified-protein anaerobic reconstitution
    exposure
    4 micromolar reductase, 20 micromolar MMACHC/CNCbl, 200 micromolar NADPH
    limitations
    Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    This flavoprotein can pass reducing power into B12 processing.
    primary_references
    [kim-2008-decyanation] Decyanation of vitamin B12 by a trafficking chaperone (2008). https://pubmed.ncbi.nlm.nih.gov/18779575/ DOI: 10.1073/pnas.0805989105
    tissue_or_cell_type
    Cell-free assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 683–695

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human purified-protein anaerobic reconstitution · source_derived_draft · unverified_draft

    ### b12-mtrr-mmachc-electrons Recombinant human MTRR with NADPH supported MMACHC-bound cyanocobalamin conversion to cob(II)alamin; free cyanocobalamin was not detectably reduced without MMACHC. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: This flavoprotein can pass reducing power into B12 processing. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Human purified-protein anaerobic reconstitution limitations: Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans. exposure: 4 micromolar reductase, 20 micromolar MMACHC/CNCbl, 200 micromolar NADPH cross_nutrient: true evidence_location: Results: Figure 4; Materials and Methods: Decyanation of CNCbl [kim-2008-decyanation] Decyanation of vitamin B12 by a trafficking chaperone (2008). https://pubmed.ncbi.nlm.nih.gov/18779575/ DOI: 10.1073/pnas.0805989105
    Complete structured claim and evidence

  4. Recombinant human NDOR1/NR1 with NADPH supported MMACHC-bound cyanocobalamin conversion to cob(II)alamin; free cyanocobalamin was not detectably reduced without MMACHC.

    Human NADPH-dependent diflavin oxidoreductase 1 → Human MMACHC / cobalamin-processing protein CblC source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Results: Figure 4; Materials and Methods: Decyanation of CNCbl
    experimental_model
    Human purified-protein anaerobic reconstitution
    exposure
    4 micromolar reductase, 20 micromolar MMACHC/CNCbl, 200 micromolar NADPH
    limitations
    Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    This flavoprotein can pass reducing power into B12 processing.
    primary_references
    [kim-2008-decyanation] Decyanation of vitamin B12 by a trafficking chaperone (2008). https://pubmed.ncbi.nlm.nih.gov/18779575/ DOI: 10.1073/pnas.0805989105
    tissue_or_cell_type
    Cell-free assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 697–709

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human purified-protein anaerobic reconstitution · source_derived_draft · unverified_draft

    ### b12-ndor1-mmachc-electrons Recombinant human NDOR1/NR1 with NADPH supported MMACHC-bound cyanocobalamin conversion to cob(II)alamin; free cyanocobalamin was not detectably reduced without MMACHC. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: This flavoprotein can pass reducing power into B12 processing. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Human purified-protein anaerobic reconstitution limitations: Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans. exposure: 4 micromolar reductase, 20 micromolar MMACHC/CNCbl, 200 micromolar NADPH cross_nutrient: true evidence_location: Results: Figure 4; Materials and Methods: Decyanation of CNCbl [kim-2008-decyanation] Decyanation of vitamin B12 by a trafficking chaperone (2008). https://pubmed.ncbi.nlm.nih.gov/18779575/ DOI: 10.1073/pnas.0805989105
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. In the human MMACHC dealkylation study, cysteine and homocysteine did not substitute for glutathione as the thiol co-substrate.

    GSH → MMACHC-catalyzed alkylcobalamin dealkylation source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Primary abstract; indexed article Introduction/Figure 1
    experimental_model
    Purified human MMACHC thiol substitution assays
    exposure
    GSH versus cysteine or homocysteine
    limitations
    No implication that cysteine availability is irrelevant to cellular GSH synthesis; that upstream pathway was not tested here.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Having a thiol group was not enough; the enzyme required glutathione in these assays.
    primary_references
    [kim-2009-gsh-dealkylation] A human vitamin B12 trafficking protein uses glutathione transferase activity for processing alkylcobalamins (2009). https://pubmed.ncbi.nlm.nih.gov/19801555/ DOI: 10.1074/jbc.M109.057877
    tissue_or_cell_type
    Cell-free assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 739–751

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human MMACHC thiol substitution assays · source_derived_draft · unverified_draft

    ### b12-mmachc-thiol-specificity In the human MMACHC dealkylation study, cysteine and homocysteine did not substitute for glutathione as the thiol co-substrate. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Having a thiol group was not enough; the enzyme required glutathione in these assays. organism: Homo sapiens tissue_or_cell_type: Cell-free assay experimental_model: Purified human MMACHC thiol substitution assays limitations: No implication that cysteine availability is irrelevant to cellular GSH synthesis; that upstream pathway was not tested here. exposure: GSH versus cysteine or homocysteine cross_nutrient: true evidence_location: Primary abstract; indexed article Introduction/Figure 1 [kim-2009-gsh-dealkylation] A human vitamin B12 trafficking protein uses glutathione transferase activity for processing alkylcobalamins (2009). https://pubmed.ncbi.nlm.nih.gov/19801555/ DOI: 10.1074/jbc.M109.057877
    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.

    Evidence, AI assistance and curation standards