25-Hydroxyvitamin D3 1-alpha-Hydroxylase

**Definition:** 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).

**Tree numbers:** - D08.244.453.499.500 - D08.244.453.915.400 - D08.811.682.690.708.170.493.500 - D08.811.682.690.708.170.915.400 - D12.776.422.220.453.499.500 - D12.776.422.220.453.915.400

**Synonyms:** - 25-Hydroxycholecalciferol-1-Hydroxylase - 25-Hydroxycholecalciferol 1-Hydroxylase - Calcidiol 1-Monooxygenase - 25-Hydroxyvitamin D(3) 1 alpha-Hydroxylase - 25-Hydroxyvitamin D2 1-hydroxylase - CYP27B1 - Cytochrome P-450 CYP27B1 - 25-Hydroxyergocalciferol 1-alpha-Hydroxylase - 25-Hydroxyvitamin D 1-alpha-Hydroxylase