| abstract |
cytochrome P450 family 27, subfamily B, polypeptide 1, also called calcidiol 1-monooxygenase. Cytochrome p450 27B1 (CYP27B1) is also called calcidiol 1-monooxygenase (EC 1.14.15.18), 25-hydroxyvitamin D(3) 1-alpha-hydroxylase (VD3 1A hydroxylase), 25-hydroxyvitamin D-1 alpha hydroxylase, 25-OHD-1 alpha-hydroxylase, 25-hydroxycholecalciferol 1-hydroxylase, or 25-hydroxycholecalciferol 1-monooxygenase. It catalyzes the conversion of 25-hydroxyvitamin D3 (25(OH)D3) to 1-alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3 or calcitriol), and of 24,25-dihydroxyvitamin D3 (24,25(OH)(2)D3) to 1-alpha,24,25-trihydroxyvitamin D3 (1alpha,24,25(OH)(3)D3). It is also active with 25-hydroxy-24-oxo-vitamin D3, and has an important role in normal bone growth, calcium metabolism, and tissue differentiation. CYP27B1 belongs to the large cytochrome P450 (P450, CYP) superfamily of heme-containing proteins that catalyze a variety of oxidative reactions of a large number of structurally different endogenous and exogenous compounds in organisms from all major domains of life. CYPs bind their diverse ligands in a buried, hydrophobic active site, which is accessed through a substrate access channel formed by two flexible helices and their connecting loop. |