{"id":"7e91d347-c1e7-5ad1-a0d6-abec71c7c6a5","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-mmachc-methyl-dealkylation","predicate":"glutathione-dependently-dealkylates","statement":"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.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"ebecd8d7-5074-5846-b1e5-5eac7c93ba7d","mechanism_event_label":"Glutathione receives the side group removed from this B12 form.","subject":{"id":"70ae4c83-37b2-5bd7-931d-021cace41eef","slug":"mmachc","display_name":"Human MMACHC / cobalamin-processing protein CblC","entity_type_key":"protein"},"object":{"id":"6563fbad-ebdc-5408-966a-d24f8b8cd854","slug":"methylcobalamin","display_name":"Methylcobalamin","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"ebecd8d7-5074-5846-b1e5-5eac7c93ba7d","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-mmachc-methyl-dealkylation-event","event_type":"biochemical_relationship","label":"Glutathione receives the side group removed from this B12 form.","description":"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.","status":"provisional","compartment":{"slug":"cytosol","display_name":"Cytosol"},"participants":[{"entity":{"id":"b44c9e27-4bbb-52d3-a022-14cddded5073","slug":"glutathione","display_name":"GSH","entity_type_key":"small_molecule"},"role":"nucleophilic co-substrate","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"227597d2-ecb7-5a01-8acc-fa6a2ff5d9ff","slug":"cob-i-alamin","display_name":"Cob(I)alamin","entity_type_key":"small_molecule"},"role":"initial cobalamin product","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"cefce950-b946-53e3-9f5b-10c7ae218fd3","slug":"s-methylglutathione","display_name":"S-Methylglutathione","entity_type_key":"small_molecule"},"role":"thioether product","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"70ae4c83-37b2-5bd7-931d-021cace41eef","slug":"mmachc","display_name":"Human MMACHC / cobalamin-processing protein CblC","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"6563fbad-ebdc-5408-966a-d24f8b8cd854","slug":"methylcobalamin","display_name":"Methylcobalamin","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"true","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_location","value_text":"Primary abstract; indexed article Introduction/Figure 1","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified human MMACHC substrate chemistry","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Specified alkylcobalamin plus GSH; kinetic temperature 20 C","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Glutathione receives the side group removed from this B12 form.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[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","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Cell-free assay","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"ca1c6cdf-ef65-5278-9964-11e8e4c327d3","evidence_kind":"source_excerpt","locator":"Lines 711-723","start_line":711,"end_line":723,"excerpt":"### b12-mmachc-methyl-dealkylation\nHuman 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.\nCondition category: normal\nnutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Glutathione receives the side group removed from this B12 form.\norganism: Homo sapiens\ntissue_or_cell_type: Cell-free assay\nexperimental_model: Purified human MMACHC substrate chemistry\nlimitations: Reconstituted biochemical system; establishes reaction capability rather than the quantitatively dominant pathway in living humans.\nexposure: Specified alkylcobalamin plus GSH; kinetic temperature 20 C\ncross_nutrient: true\nevidence_location: Primary abstract; indexed article Introduction/Figure 1\n[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","model_system":"Purified human MMACHC substrate chemistry","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study 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","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"73145023-2982-5848-aff2-8d8875d6b9c5","stable_key":"import-7fc92b9e-9cbf-556e-8719-6b5244625250","title":"Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text.","file_path":"","sha256":"ad5b3a51d36e856aa7fdfd1cc23f690b094689bad87d28e1a621a54675a01c92","revision_id":"118bd616-0c13-549f-bfeb-bc439715b89c","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}