Comparison of 12α-hydroxylation of oxygenated 5α-cholestanes and allochenodeoxycholate with rat liver microsomes

摘要: [5alpha,6alpha-3H2]-5alpha-Cholestane-3alpha,7alpha-diol (A), (25 R)-3alpha,7alpha-dihydroxyl-[5alpha,6alpha-3H2]-5alpha--cholestan-26-oic acid (B),(25R)-[5alpha,6alpha-3H2]stane-3alpha,7alpha-26-triol (C), and [3beta-3H]allochenodeoxycholic (D) were prepared, characterized, studied with a rat liver microsomal preparation fortified 1 mM NADPH. The 12alpha-hydroxylated product formed from each of these substrates was identified by isotopic dilution; the relative reactivity four (A) 100; (B) 87; (C) 135; 40. system showed requirement for added NADPH other properties similar to those shown 12alpha-hydroxylation 7alpha-hydroxycholest-4-en-3-one, which is ultimately converted cholic acid. Since coplanar 5alpha-cholestane-3alpha,7alpha-diol virtually superimposable upon enzymic requirements are comparable, it suggested that single enzyme may be responsible substrates.