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:2026586, PubMed:16617161, PubMed:10231362). 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). calcitriol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = calcitetrol + H2O + 2 oxidized [adrenodoxin] calcitetrol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = (1S)-1,25-dihydroxy-24-oxocalciol + 2 H2O + 2 oxidized [adrenodoxin] (1S)-1,25-dihydroxy-24-oxocalciol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = (1S)-1,23,25-trihydroxy-24-oxocalciol + H2O + 2 oxidized [adrenodoxin] (1S)-1,23-dihydroxy-24,25,26,27-tetranorcalciol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = (1S)-1-hydroxy-23-oxo-24,25,26,27-tetranorcalciol + 2 H2O + 2 oxidized [adrenodoxin] (1S)-1-hydroxy-23-oxo-24,25,26,27-tetranorcalciol + H(+) + O2 + 2 reduced [adrenodoxin] = calcitroate + H2O + 2 oxidized [adrenodoxin] calcidiol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = H2O + 2 oxidized [adrenodoxin] + secalciferol 2 H(+) + O2 + 2 reduced [adrenodoxin] + secalciferol = 25-hydroxy-24-oxocalciol + 2 H2O + 2 oxidized [adrenodoxin] 25-hydroxy-24-oxocalciol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = 23S,25-dihydroxy-24-oxocholecalciferol + H2O + 2 oxidized [adrenodoxin] 20S,23-dihydroxycholecalciferol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = 20S,23,25-trihydroxycholecalciferol + H2O + 2 oxidized [adrenodoxin] 20S,23-dihydroxycholecalciferol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = 20S,23,24-trihydroxycholecalciferol + H2O + 2 oxidized [adrenodoxin] 20S-hydroxycholecalciferol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = 20S,25-dihydroxycholecalciferol + H2O + 2 oxidized [adrenodoxin] 20S-hydroxycholecalciferol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = 20S,24S-dihydroxycholecalciferol + H2O + 2 oxidized [adrenodoxin] 20S-hydroxycholecalciferol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = 20S,24R-dihydroxycholecalciferol + H2O + 2 oxidized [adrenodoxin] Optimum pH is 7.7. Belongs to the cytochrome P450 family.