Conversion of 7α,12α-dihydroxycholest-4-en-3-one to 5α-cholestane-3α,7α,12α-triol by iguana liver microsomes

Abstract

The role of 7α,l2α-dihydroxycholest-4-en-3-one as an intermediate in the formation of 5α-bile acids from cholesterol was investigated with liver preparations of Iguana iguana in vitro. The microsomal fraction of iguana liver catalyzed the transformation of 7α,12α-dihydroxycholest-4-en-3-one to 5α-cholestane-3α,7α,l2α-triol in good yield. 7α,l2α-dihydroxy-5α-cholestan-3-one served as an intermediate. Under the conditions employed, formation of the corresponding 5β-isomers could not be detected. High speed supernatant solution and mitochondrial fraction of iguana liver did not reduce 7α,12α-dihydroxycholest-4-en-3-one to a measurable extent. The microsomal enzyme system required NADPH as hydrogen donor and was inactive in the presence of NADH.It is suggested that 7α,l2α-dihydroxycholest-4-en-3-one may serve as a common intermediate in the formation of 5α- and 5β-bile acids from cholesterol.

Keywords

• Iguana iguana
• allo bile acids
• biosynthesis
• liver microsomes
• 7α,l2α-dihydroxycholest-4-en-3-one
• 7α,12α-dihydroxy-5α-cholestan-3-one