title: Identification of 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholest-24-enoic acid as an intermediate in the peroxisomal conversion of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid to cholic acid.
abstract: In this study, we have identified a delta 24-unsaturated intermediate involved in the conversion of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid to cholic acid by the peroxisomal fraction of rat liver. An accumulation of this intermediate was observed when NAD+ was omitted from the reaction mixture. The intermediate was isolated by reversed-phase high-pressure liquid chromatography and identified by combined gas-liquid chromatography-mass spectrometry. The peroxisomal fraction was able to catalyze the conversion of the delta 24-unsaturated intermediate to cholic acid in the presence of CoA, ATP, Mg2+ and NAD+. The identification of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholest-24-enoic acid in cholic acid formation supports the proposed reaction mechanism in which the side-chain cleavage of C27-steroids is similar to that of peroxisomal beta-oxidation of fatty acids. This involves an FAD-dependent oxidase acting on 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoyl-CoA.
authors.affiliation: Institute for Nutrition Research, School of Medicine, University of Oslo, Norway.
authors.forename: A K
authors.initials: AK
authors.lastname: Ostlund Farrants
authors.forename: I
authors.initials: I
authors.lastname: Björkhem
authors.forename: J I
authors.initials: JI
authors.lastname: Pedersen
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002777:Cholestanols / Q000378:metabolism*; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000378:metabolism; D019826:Cholic Acid; D002793:Cholic Acids / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003065:Coenzyme A / Q000494:pharmacology; D008401:Gas Chromatography-Mass Spectrometry; D008099:Liver / Q000648:ultrastructure*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008830:Microbodies / Q000378:metabolism*; D009243:NAD / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002777:Cholestanols; D002793:Cholic Acids; D009243:NAD; C059108:3,7,12-trihydroxycholest-24-enoic acid; C022069:3,7,12-trihydroxycholestan-26-oic acid; D000255:Adenosine Triphosphate; D002784:Cholesterol; D019826:Cholic Acid; D008274:Magnesium; D003065:Coenzyme A