Vitamin D 25-hydroxylase - Four decades of searching, are we there yet?

Bioactivation of vitamin D-3 involves 25-hydroxylation and subsequent 1 alpha-hydroxylation to produce 1 alpha,25-dihydroxyvitamin D-3 [1,25(OH)(2)D-3], the active hormone. six cytochrome P450 enzymes (CYP27A1, CYP2R1, CYP2J2/3, CYP3A4, CYP2D25 and CYP2C11) catalyzing the initial 25-hydroxylation step are reviewed, and their physiological relevance as vitamin D 25-hydroxylases in vivo is discussed. (C) 2012 Elsevier Inc. All rights reserved.