{"id":"b372cfba-6aab-56d5-aa42-587a38e0d251","stable_key":"1deb434a-3547-51a0-a038-87b1ce79ec38:vd-act-cyp27a1-d3","predicate":"produces","statement":"Human CYP27A1 catalyzed D3 25-hydroxylation in the recombinant comparison, with lower catalytic efficiency than CYP2R1.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"8e9ea650-5b65-5dab-84f0-2a742f40ff4e","mechanism_event_label":"A second enzyme can 25-hydroxylate D3 in laboratory assays.","subject":{"id":"a51f023f-7880-5e68-a72b-00293792ff64","slug":"cyp27a1","display_name":"Human sterol 27-hydroxylase / CYP27A1","entity_type_key":"protein"},"object":{"id":"6bd73bd2-1f0a-5caa-ba69-7ce1b75364bb","slug":"calcifediol","display_name":"Calcifediol / 25-hydroxyvitamin D3","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"8e9ea650-5b65-5dab-84f0-2a742f40ff4e","stable_key":"1deb434a-3547-51a0-a038-87b1ce79ec38:vd-act-cyp27a1-d3-event","event_type":"biochemical_relationship","label":"A second enzyme can 25-hydroxylate D3 in laboratory assays.","description":"Human CYP27A1 catalyzed D3 25-hydroxylation in the recombinant comparison, with lower catalytic efficiency than CYP2R1.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"a51f023f-7880-5e68-a72b-00293792ff64","slug":"cyp27a1","display_name":"Human sterol 27-hydroxylase / CYP27A1","entity_type_key":"protein"},"role":"enzyme","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"b162e431-b442-5400-9335-ec91f7875a4e","slug":"cholecalciferol","display_name":"Cholecalciferol","entity_type_key":"small_molecule"},"role":"substrate","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"6bd73bd2-1f0a-5caa-ba69-7ce1b75364bb","slug":"calcifediol","display_name":"Calcifediol / 25-hydroxyvitamin D3","entity_type_key":"small_molecule"},"role":"product","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":"Primary abstract, substrate product positions and kinetic comparison.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Recombinant human CYP27A1/CYP2R1 comparison","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Kinetic substrate comparison; CYP2R1 kcat/Km was reported 26-fold higher in this assay.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Does not establish CYP27A1 as the dominant human liver D3 25-hydroxylase.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient","value_text":"Vitamin D2 and D3","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-d","display_name":"Vitamin D2 and D3","entity_type_key":"chemical_species"}},{"dimension":"nutrient_topic","value_text":"Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-d","display_name":"Vitamin D2 and D3","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens protein","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"A second enzyme can 25-hydroxylate D3 in laboratory assays.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[shinkyo2004] Metabolism of vitamin D by human microsomal CYP2R1. (2004). https://pubmed.ncbi.nlm.nih.gov/15465040/ DOI: 10.1016/j.bbrc.2004.09.073","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"mitochondrial enzyme preparation","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"c8729eee-0fb7-5a72-b75b-f709f7156ab9","evidence_kind":"source_excerpt","locator":"Lines 317-330","start_line":317,"end_line":330,"excerpt":"### vd-act-cyp27a1-d3\nHuman CYP27A1 catalyzed D3 25-hydroxylation in the recombinant comparison, with lower catalytic efficiency than CYP2R1.\nCondition category: normal\nnutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: A second enzyme can 25-hydroxylate D3 in laboratory assays.\norganism: Homo sapiens protein\ntissue_or_cell_type: mitochondrial enzyme preparation\nexperimental_model: Recombinant human CYP27A1/CYP2R1 comparison\nlimitations: Does not establish CYP27A1 as the dominant human liver D3 25-hydroxylase.\nexposure: Kinetic substrate comparison; CYP2R1 kcat/Km was reported 26-fold higher in this assay.\ncross_nutrient: false\nevidence_location: Primary abstract, substrate product positions and kinetic comparison.\nnutrient: Vitamin D2 and D3\n[shinkyo2004] Metabolism of vitamin D by human microsomal CYP2R1. (2004). https://pubmed.ncbi.nlm.nih.gov/15465040/ DOI: 10.1016/j.bbrc.2004.09.073","model_system":"Recombinant human CYP27A1/CYP2R1 comparison","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [shinkyo2004] Metabolism of vitamin D by human microsomal CYP2R1. (2004). https://pubmed.ncbi.nlm.nih.gov/15465040/ DOI: 10.1016/j.bbrc.2004.09.073","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"c95c763c-5b31-5b3f-a2f8-2dfe5ef0d3ca","stable_key":"import-1deb434a-3547-51a0-a038-87b1ce79ec38","title":"Vitamin D2 and D3: 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":"51004bf0d78db6146b8f198b0688a3cc7d4ea9822415a9c034f4c8790fb4e38b","revision_id":"d52ff207-a311-5f24-96f4-462838792db5","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}