Component

Cob(II)alamin

Cob(II)alamin; distinguish intact cobalamin-bound cobalt from free cobalt ion. Cobalamin corrinoid with cobalt in oxidation state +2; not free cobalt ion.

12 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

Where it participates (unsigned role)

  1. ADP binding protected cob(II)alamin on human MMUT from air oxidation by stabilizing a solvent-shielded conformation.

    Adenosine diphosphate → Overoxidation of human MMUT-bound cob(II)alamin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Full text Results; Figures 2-3, Table 3
    experimental_model
    Purified human proteins
    exposure
    ADP added to MMUT-bound cob(II)alamin under air
    limitations
    Structural/biochemical protection does not establish regulation by cellular energy charge.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    ADP helped preserve an inactive B12 cofactor for repair in the human-protein assay.
    primary_references
    [gouda-2023-adp-repair] Bivalent molecular mimicry by ADP protects metal redox state and promotes coenzyme B12 repair. (2023). https://pubmed.ncbi.nlm.nih.gov/36888659/ DOI: 10.1073/pnas.2220677120
    tissue_or_cell_type
    Purified protein assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1398–1410

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

    ### adp-protects-mmut-cofactor-redox ADP binding protected cob(II)alamin on human MMUT from air oxidation by stabilizing a solvent-shielded conformation. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: ADP helped preserve an inactive B12 cofactor for repair in the human-protein assay. organism: Homo sapiens tissue_or_cell_type: Purified protein assay experimental_model: Purified human proteins limitations: Structural/biochemical protection does not establish regulation by cellular energy charge. exposure: ADP added to MMUT-bound cob(II)alamin under air cross_nutrient: false evidence_location: Full text Results; Figures 2-3, Table 3 [gouda-2023-adp-repair] Bivalent molecular mimicry by ADP protects metal redox state and promotes coenzyme B12 repair. (2023). https://pubmed.ncbi.nlm.nih.gov/36888659/ DOI: 10.1073/pnas.2220677120
    Complete structured claim and evidence

  2. Under anaerobic conditions, ADP reduced the rate of cob(II)alamin transfer from human MMUT to MMAB in the MMAA repair system.

    Adenosine diphosphate → Cob(II)alamin off-loading from human MMUT source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Full text Results; Figures 2-3, Table 3
    experimental_model
    Purified human proteins
    exposure
    Anaerobic cofactor-transfer assay with ADP
    limitations
    Transfer rate differs from oxidation protection; methylmalonyl-CoA reversed ADP inhibition in this assay.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    When oxidation was excluded, ADP slowed transfer of inactive B12 between the purified human proteins.
    primary_references
    [gouda-2023-adp-repair] Bivalent molecular mimicry by ADP protects metal redox state and promotes coenzyme B12 repair. (2023). https://pubmed.ncbi.nlm.nih.gov/36888659/ DOI: 10.1073/pnas.2220677120
    tissue_or_cell_type
    Purified protein assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1412–1424

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

    ### adp-slows-mmut-cob-ii-offloading Under anaerobic conditions, ADP reduced the rate of cob(II)alamin transfer from human MMUT to MMAB in the MMAA repair system. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: When oxidation was excluded, ADP slowed transfer of inactive B12 between the purified human proteins. organism: Homo sapiens tissue_or_cell_type: Purified protein assay experimental_model: Purified human proteins limitations: Transfer rate differs from oxidation protection; methylmalonyl-CoA reversed ADP inhibition in this assay. exposure: Anaerobic cofactor-transfer assay with ADP cross_nutrient: false evidence_location: Full text Results; Figures 2-3, Table 3 [gouda-2023-adp-repair] Bivalent molecular mimicry by ADP protects metal redox state and promotes coenzyme B12 repair. (2023). https://pubmed.ncbi.nlm.nih.gov/36888659/ DOI: 10.1073/pnas.2220677120
    Complete structured claim and evidence

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. Human [2Fe-2S] ferredoxin FDX1 supplied electrons for MMAB-dependent adenosylcobalamin synthesis in the FDXR/NADPH reconstitution.

    Human adrenodoxin / FDX1 → Human ATP:cob(I)alamin adenosyltransferase / MMAB source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Abstract and indexed primary Results, Figure 3
    experimental_model
    Purified human proteins
    exposure
    FDX1, FDXR and NADPH with MMAB, cob(II)alamin and ATP
    limitations
    Biochemically competent donor; exclusivity or necessity in living humans was not tested.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    In the purified human system, an iron-sulfur electron carrier supported B12 activation.
    primary_references
    [gouda-2023-mmab-redox] Coordination Chemistry Controls Coenzyme B12 Synthesis by Human Adenosine Triphosphate:Cob(I)alamin Adenosyltransferase. (2023). https://pubmed.ncbi.nlm.nih.gov/37526260/ DOI: 10.1021/acs.inorgchem.3c02163
    tissue_or_cell_type
    Purified protein assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1005–1017

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

    ### fdx1-supports-mmab Human [2Fe-2S] ferredoxin FDX1 supplied electrons for MMAB-dependent adenosylcobalamin synthesis in the FDXR/NADPH reconstitution. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: In the purified human system, an iron-sulfur electron carrier supported B12 activation. organism: Homo sapiens tissue_or_cell_type: Purified protein assay experimental_model: Purified human proteins limitations: Biochemically competent donor; exclusivity or necessity in living humans was not tested. exposure: FDX1, FDXR and NADPH with MMAB, cob(II)alamin and ATP cross_nutrient: true evidence_location: Abstract and indexed primary Results, Figure 3 [gouda-2023-mmab-redox] Coordination Chemistry Controls Coenzyme B12 Synthesis by Human Adenosine Triphosphate:Cob(I)alamin Adenosyltransferase. (2023). https://pubmed.ncbi.nlm.nih.gov/37526260/ DOI: 10.1021/acs.inorgchem.3c02163
    Complete structured claim and evidence

  10. Itaconyl-CoA inactivated purified human MMUT by forming a stable adduct with the B12-derived deoxyadenosyl moiety.

    Itaconyl-CoA → Human methylmalonyl-CoA mutase / MMUT source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Primary abstract; indexed Results and Figure 3E
    experimental_model
    Purified human MMUT; inhibitor-product spectroscopy and analysis
    exposure
    Itaconyl-CoA exposure in the purified-enzyme assay
    limitations
    Mechanism-based inhibitor is distinct from physiological methylmalonyl-CoA; no human dietary effect inferred.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    The itaconyl-CoA experiment trapped B12 radical chemistry and stopped the purified human enzyme.
    primary_references
    [ruetz-2019-itaconyl-radical] Itaconyl-CoA forms a stable biradical in methylmalonyl-CoA mutase and derails its activity and repair. (2019). https://pubmed.ncbi.nlm.nih.gov/31672889/ DOI: 10.1126/science.aay0934
    tissue_or_cell_type
    Purified protein assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1384–1396

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human MMUT; inhibitor-product spectroscopy and analysis · source_derived_draft · unverified_draft

    ### itaconyl-coa-inactivates-human-mmut Itaconyl-CoA inactivated purified human MMUT by forming a stable adduct with the B12-derived deoxyadenosyl moiety. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: The itaconyl-CoA experiment trapped B12 radical chemistry and stopped the purified human enzyme. organism: Homo sapiens tissue_or_cell_type: Purified protein assay experimental_model: Purified human MMUT; inhibitor-product spectroscopy and analysis limitations: Mechanism-based inhibitor is distinct from physiological methylmalonyl-CoA; no human dietary effect inferred. exposure: Itaconyl-CoA exposure in the purified-enzyme assay cross_nutrient: false evidence_location: Primary abstract; indexed Results and Figure 3E [ruetz-2019-itaconyl-radical] Itaconyl-CoA forms a stable biradical in methylmalonyl-CoA mutase and derails its activity and repair. (2019). https://pubmed.ncbi.nlm.nih.gov/31672889/ DOI: 10.1126/science.aay0934
    Complete structured claim and evidence

  11. A human MMAA/MMAB repair mixture with GTP and ATP transferred cob(II)alamin from MMUT to MMAB in anaerobic spectroscopy.

    Human MMAA GTPase → Cob(II)alamin off-loading from human MMUT source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Full text Results; Figures 2-4; cofactor off-loading and MMUT activity Methods
    experimental_model
    Purified human proteins
    exposure
    Anaerobic assay; MMAB, MMAA, GTP and ATP
    limitations
    Reconstituted transfer; spectroscopy reports cofactor environment, not cellular turnover.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    In the purified repair assay, inactive B12 moved from MMUT back to MMAB.
    primary_references
    [mascarenhas-2023-nanoassembly] Architecture of the human G-protein-methylmalonyl-CoA mutase nanoassembly for B12 delivery and repair. (2023). https://pubmed.ncbi.nlm.nih.gov/37468522/ DOI: 10.1038/s41467-023-40077-4
    tissue_or_cell_type
    Purified protein assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1131–1143

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

    ### mmaa-mmab-offload-cob-ii A human MMAA/MMAB repair mixture with GTP and ATP transferred cob(II)alamin from MMUT to MMAB in anaerobic spectroscopy. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: In the purified repair assay, inactive B12 moved from MMUT back to MMAB. organism: Homo sapiens tissue_or_cell_type: Purified protein assay experimental_model: Purified human proteins limitations: Reconstituted transfer; spectroscopy reports cofactor environment, not cellular turnover. exposure: Anaerobic assay; MMAB, MMAA, GTP and ATP cross_nutrient: false evidence_location: Full text Results; Figures 2-4; cofactor off-loading and MMUT activity Methods [mascarenhas-2023-nanoassembly] Architecture of the human G-protein-methylmalonyl-CoA mutase nanoassembly for B12 delivery and repair. (2023). https://pubmed.ncbi.nlm.nih.gov/37468522/ DOI: 10.1038/s41467-023-40077-4
    Complete structured claim and evidence

  12. Purified human MTRR coupled cob(II)alamin reduction to MMAB-dependent adenosylcobalamin synthesis in vitro.

    Methionine synthase reductase / MTRR → Human ATP:cob(I)alamin adenosyltransferase / MMAB source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    true
    evidence_location
    Indexed primary abstract
    experimental_model
    Purified human proteins
    exposure
    Purified MTRR plus MMAB and reductants
    limitations
    MTRR coupling in vitro does not identify the physiological mitochondrial electron donor.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Human MTRR supported B12 activation in a test-tube system; this does not establish its mitochondrial role.
    primary_references
    [leal-2004-human-mmab] Human ATP:Cob(I)alamin adenosyltransferase and its interaction with methionine synthase reductase. (2004). https://pubmed.ncbi.nlm.nih.gov/15347655/ DOI: 10.1074/jbc.m405449200
    tissue_or_cell_type
    Purified protein assay

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 991–1003

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

    ### mtrr-supports-mmab-in-vitro Purified human MTRR coupled cob(II)alamin reduction to MMAB-dependent adenosylcobalamin synthesis in vitro. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Human MTRR supported B12 activation in a test-tube system; this does not establish its mitochondrial role. organism: Homo sapiens tissue_or_cell_type: Purified protein assay experimental_model: Purified human proteins limitations: MTRR coupling in vitro does not identify the physiological mitochondrial electron donor. exposure: Purified MTRR plus MMAB and reductants cross_nutrient: true evidence_location: Indexed primary abstract [leal-2004-human-mmab] Human ATP:Cob(I)alamin adenosyltransferase and its interaction with methionine synthase reductase. (2004). https://pubmed.ncbi.nlm.nih.gov/15347655/ DOI: 10.1074/jbc.m405449200
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