Vitamin D 25-hydroxylase is a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. Found in the liver, this enzyme is a microsomal vitamin D hydroxylase that converts vitamin D into 25-hydroxyvitamin D (calcidiol), which is the major circulatory form of the vitamin.
Ramos-Lopez E, Brück P, Jansen T, et al. (2008). "CYP2R1 (vitamin D 25-hydroxylase) gene is associated with susceptibility to type 1 diabetes and vitamin D levels in Germans.". Diabetes Metab. Res. Rev.23 (8): 631–6. doi:10.1002/dmrr.719. PMID17607662.
Ramos-Lopez E, Brück P, Jansen T, et al. (2007). "CYP2R1-, CYP27B1- and CYP24-mRNA expression in German type 1 diabetes patients.". J. Steroid Biochem. Mol. Biol.103 (3–5): 807–10. doi:10.1016/j.jsbmb.2006.12.056. PMID17223345.