{"id":"98996fda-d98c-5bf2-a6d5-743948a18ff7","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-mmad-free-aquo-binding","predicate":"binds","statement":"Reduced, full-length human MMADHC bound free aquocobalamin in vitro with a reported KD of 1.0 +/- 0.4 micromolar and formed a base-on thiolato-cob(III)alamin species.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"49927fe9-195f-5f58-8e70-1c87005ce703","mechanism_event_label":"MMADHC could bind this B12 form directly under the preparation conditions.","subject":{"id":"c0fe6bd6-68d8-5ab4-a062-e9f4c70f94a3","slug":"mmadhc","display_name":"Human MMADHC / cobalamin-trafficking protein CblD","entity_type_key":"protein"},"object":{"id":"404d4448-1fbd-50d3-9bf5-573dbf188cb0","slug":"aquocobalamin","display_name":"Aquocobalamin","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"49927fe9-195f-5f58-8e70-1c87005ce703","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-mmad-free-aquo-binding-event","event_type":"biochemical_relationship","label":"MMADHC could bind this B12 form directly under the preparation conditions.","description":"Reduced, full-length human MMADHC bound free aquocobalamin in vitro with a reported KD of 1.0 +/- 0.4 micromolar and formed a base-on thiolato-cob(III)alamin species.","status":"provisional","compartment":{"slug":"cytosol","display_name":"Cytosol"},"participants":[{"entity":{"id":"88c49063-bdbd-5fdd-bfe1-da1541c79c8f","slug":"mmachc-mmadhc-cobalamin-complex","display_name":"Human MMACHC–MMADHC cobalamin coordination complex","entity_type_key":"protein_complex"},"role":"downstream comparison","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"c0fe6bd6-68d8-5ab4-a062-e9f4c70f94a3","slug":"mmadhc","display_name":"Human MMADHC / cobalamin-trafficking protein CblD","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"404d4448-1fbd-50d3-9bf5-573dbf188cb0","slug":"aquocobalamin","display_name":"Aquocobalamin","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"false","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_location","value_text":"Abstract; indexed Results: CblD binds H2OCbl and forms a complex with CblC","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human full-length recombinant MMADHC binding assay","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Reduction of cysteines followed by removal of excess DTT; free aquocobalamin","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Slow binding and micromolar affinity make free aquocobalamin capture an uncertain physiological route; older no-binding results were condition-sensitive.","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":"MMADHC could bind this B12 form directly under the preparation conditions.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[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","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":"442ceab2-84c1-5e23-891a-7aff49263586","evidence_kind":"source_excerpt","locator":"Lines 893-905","start_line":893,"end_line":905,"excerpt":"### b12-mmad-free-aquo-binding\nReduced, full-length human MMADHC bound free aquocobalamin in vitro with a reported KD of 1.0 +/- 0.4 micromolar and formed a base-on thiolato-cob(III)alamin species.\nCondition category: normal\nnutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: MMADHC could bind this B12 form directly under the preparation conditions.\norganism: Homo sapiens\ntissue_or_cell_type: Cell-free assay\nexperimental_model: Human full-length recombinant MMADHC binding assay\nlimitations: Slow binding and micromolar affinity make free aquocobalamin capture an uncertain physiological route; older no-binding results were condition-sensitive.\nexposure: Reduction of cysteines followed by removal of excess DTT; free aquocobalamin\ncross_nutrient: false\nevidence_location: Abstract; indexed Results: CblD binds H2OCbl and forms a complex with CblC\n[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","model_system":"Human full-length recombinant MMADHC binding assay","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study 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","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}