A mitochondrial cytochrome P450 enzyme that catalyzes the 1-alpha-hydroxylation of 25-hydroxyvitamin D3 (also known as 25-hydroxycholecalciferol) in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP27B1 gene, converts 25-hydroxyvitamin D3 to 1-alpha,25-dihydroxyvitamin D3 which is the active form of VITAMIN D in regulating bone growth and calcium metabolism. This enzyme is also active on plant 25-hydroxyvitamin D2 (ergocalciferol).

Synonyms: EC 1.14.15.18 25-Hydroxyvitamin D2 1-hydroxylase 25-Hydroxycholecalciferol-1-Hydroxylase 25 Hydroxyvitamin D 1 alpha Hydroxylase Calcidiol 1 Monooxygenase Cytochrome P 450 CYP27B1 1-hydroxylase, 25-Hydroxyvitamin D2 25 Hydroxycholecalciferol 1 Hydroxylase 25 Hydroxyvitamin D3 1 alpha Hydroxylase 25-Hydroxycholecalciferol 1-Hydroxylase 1-alpha-Hydroxylase, 25-Hydroxyergocalciferol 25 Hydroxyergocalciferol 1 alpha Hydroxylase 25-Hydroxyvitamin D3 1-alpha-Hydroxylase Cytochrome P-450 CYP27B1 CYP27B1 1-alpha-Hydroxylase, 25-Hydroxyvitamin D 25-Hydroxyergocalciferol 1-alpha-Hydroxylase 25-Hydroxyvitamin D(3) 1 alpha-Hydroxylase 25 Hydroxyvitamin D2 1 hydroxylase Calcidiol,NADPH:oxygen oxidoreductase (1-hydroxylating) 25-Hydroxyvitamin D 1-alpha-Hydroxylase Calcidiol 1-Monooxygenase