1,25-dihydroxyvitamin D(3) 24-hydroxylase, mitochondrial

UniProtKB accession:  Q09128

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UniProtKB description:  A cytochrome P450 monooxygenase with a key role in vitamin D catabolism and calcium homeostasis. Via C24-oxidation pathway, catalyzes the inactivation of both the vitamin D precursor calcidiol (25-hydroxyvitamin D(3)) and the active hormone calcitriol (1-alpha,25-dihydroxyvitamin D(3)) (PubMed:10231362, PubMed:16617161, PubMed:2026586). With initial hydroxylation at C-24 (via C24-oxidation pathway), performs a sequential 6-step oxidation of calcitriol leading to the formation of the biliary metabolite calcitroic acid (PubMed:10231362, PubMed:16617161). Hydroxylates at C-24 or C-25 other vitamin D active metabolites, such as CYP11A1-derived secosteroids 20S-hydroxycholecalciferol and 20S,23-dihydroxycholecalciferol (PubMed:25727742). Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via FDXR/adrenodoxin reductase and FDX1/adrenodoxin (PubMed:2026586).