{"id":"bad6f0c7-077b-58bb-9e26-6a6cd1624c2f","stable_key":"548ab9d6-3a9b-5bed-879c-17d03813b636:b2-mthfr-fad-occupancy","predicate":"binds","statement":"Native mass spectrometry and crystallography identified FAD bound to recombinant human MTHFR catalytic domains.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"3650fa21-7149-5e73-ac74-23bc17ae959d","mechanism_event_label":"MTHFR carries a B2-derived FAD cofactor.","subject":{"id":"e2cd7179-f218-54e8-9ce9-7a836ae35fac","slug":"fad","display_name":"FAD","entity_type_key":"small_molecule"},"object":{"id":"9fc32b1a-0f08-544c-a361-1c728203b6ec","slug":"mthfr","display_name":"Methylenetetrahydrofolate reductase / MTHFR","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"3650fa21-7149-5e73-ac74-23bc17ae959d","stable_key":"548ab9d6-3a9b-5bed-879c-17d03813b636:b2-mthfr-fad-occupancy-event","event_type":"biochemical_relationship","label":"MTHFR carries a B2-derived FAD cofactor.","description":"Native mass spectrometry and crystallography identified FAD bound to recombinant human MTHFR catalytic domains.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"e2cd7179-f218-54e8-9ce9-7a836ae35fac","slug":"fad","display_name":"FAD","entity_type_key":"small_molecule"},"role":"bound cofactor","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"9fc32b1a-0f08-544c-a361-1c728203b6ec","slug":"mthfr","display_name":"Methylenetetrahydrofolate reductase / MTHFR","entity_type_key":"protein"},"role":"enzyme","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"B2-FAD supports a folate-processing enzyme.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_location","value_text":"Results: kinetics, FAD occupancy and SAM inhibition; Table 1; Figs 2-4, 6","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Recombinant human MTHFR expressed in Sf9 cells; mass spectrometry, 2.5-A structure, HPLC activity assays.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Purified-enzyme assay","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Biochemical evidence does not establish a dietary threshold or supplementation benefit.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Riboflavin research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"riboflavin","display_name":"Riboflavin (vitamin B2)","entity_type_key":"small_molecule"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"MTHFR carries a B2-derived FAD cofactor.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[froese2018] Structural basis for the regulation of human 5,10-methylenetetrahydrofolate reductase by phosphorylation and S-adenosylmethionine inhibition. (2018). https://pubmed.ncbi.nlm.nih.gov/29891918/ DOI: 10.1038/s41467-018-04735-2","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Purified recombinant enzyme; no intact tissue","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"24dafdab-9ad3-584c-a0ce-ba753740d2e8","evidence_kind":"source_excerpt","locator":"Lines 996-1008","start_line":996,"end_line":1008,"excerpt":"### b2-mthfr-fad-occupancy\nNative mass spectrometry and crystallography identified FAD bound to recombinant human MTHFR catalytic domains.\nCondition category: normal\nnutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: MTHFR carries a B2-derived FAD cofactor.\norganism: Homo sapiens\ntissue_or_cell_type: Purified recombinant enzyme; no intact tissue\nexperimental_model: Recombinant human MTHFR expressed in Sf9 cells; mass spectrometry, 2.5-A structure, HPLC activity assays.\nlimitations: Biochemical evidence does not establish a dietary threshold or supplementation benefit.\nexposure: Purified-enzyme assay\ncross_nutrient: B2-FAD supports a folate-processing enzyme.\nevidence_location: Results: kinetics, FAD occupancy and SAM inhibition; Table 1; Figs 2-4, 6\n[froese2018] Structural basis for the regulation of human 5,10-methylenetetrahydrofolate reductase by phosphorylation and S-adenosylmethionine inhibition. (2018). https://pubmed.ncbi.nlm.nih.gov/29891918/ DOI: 10.1038/s41467-018-04735-2","model_system":"Recombinant human MTHFR expressed in Sf9 cells; mass spectrometry, 2.5-A structure, HPLC activity assays.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [froese2018] Structural basis for the regulation of human 5,10-methylenetetrahydrofolate reductase by phosphorylation and S-adenosylmethionine inhibition. (2018). https://pubmed.ncbi.nlm.nih.gov/29891918/ DOI: 10.1038/s41467-018-04735-2","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"4f7c9578-82bf-5e2d-b5c4-72a79fb4f6af","stable_key":"import-548ab9d6-3a9b-5bed-879c-17d03813b636","title":"Riboflavin: 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":"680cb6bc8249877f2410f551807f10d390fdd719014137d7414ba3420e29228d","revision_id":"7a61e299-908d-5372-860b-99ed190f9d7a","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}