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the enzyme required glutathione in these assays.","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":"d71b23fc-f7c7-5bc2-a2bb-069fb4f7b353","evidence_kind":"source_excerpt","locator":"Lines 739-751","start_line":739,"end_line":751,"excerpt":"### b12-mmachc-thiol-specificity\nIn the human MMACHC dealkylation study, cysteine and homocysteine did not substitute for glutathione as the thiol co-substrate.\nCondition category: normal\nnutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Having a thiol group was not enough; the enzyme required glutathione in these assays.\norganism: Homo sapiens\ntissue_or_cell_type: Cell-free assay\nexperimental_model: Purified human MMACHC thiol substitution assays\nlimitations: No implication that cysteine availability is irrelevant to cellular GSH synthesis; that upstream pathway was not tested here.\nexposure: GSH versus cysteine or homocysteine\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 thiol substitution assays","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}