4-Cholesten-7alpha,27-diol-3-one is 12alpha-hydroxylated to 4-Cholesten-7alpha,12alpha,27-triol-3-one 4-Cholesten-7alpha,27-diol-3-one + NADPH + H+ + O2 => 4-Cholesten-7alpha,12alpha,27-triol-3-one + NADP+ + H2O 4-Cholesten-7alpha,27-diol-3-one, NADPH + H+, and O2 form 4-Cholesten-7alpha,12alpha,27-triol-3-one + NADP+ + H2O. This reaction is catalyzed by sterol 12alpha hydroxylase (CYP8B1), an enzyme associated with the endoplasmic reticulum membrane. While the human gene has been cloned (Gafvels et al. 1999), its protein product has not been characterized, and the enzymatic properties of human CYP8B1 protein are inferred from those of its well-characterized rabbit homolog (Ishida et al. 1992). Authored: Jassal, B, 2008-05-19 12:57:01 EC Number: 1.14.13.95 Edited: D'Eustachio, P, 2007-02-27 21:49:11 Pubmed10051404 Pubmed1400444 Reactome Database ID Release 43193845 Reactome, http://www.reactome.org ReactomeREACT_10028 Reviewed: D'Eustachio, P, 2008-05-28 08:30:54