Hydroxylates vitamin D(3) into 25-hydroxyvitamin D(3) and 1-alpha,25-dihydroxyvitamin D(3), its physiologically active forms. It first hydroxylates the C-25 position of vitamin D(3) to form 25-hydroxyvitamin D(3), then subsequently hydroxylates the C-1-alpha position to form 1-alpha,25-dihydroxyvitamin D(3). Also displays 25-hydroxylase activity on vitamin D(2) and 7-dehydrocholesterol. May play a role in the biosynthesis of steroid metabolic intermediates. 5beta-cholestane-3alpha,7alpha,12alpha-triol + 5 H(+) + 3 O2 + 6 reduced [adrenodoxin] = (25R)-3alpha,7alpha,12alpha-trihydroxy-5beta-cholestan-26-oate + 4 H2O + 6 oxidized [adrenodoxin] Activated by partially methylated beta-cyclodextrin. Belongs to the cytochrome P450 family.