title: Conjugation reactions catalyzed by bifunctional proteins related to beta-oxidation in bile acid biosynthesis.
abstract: The conjugation reactions of hydration and dehydrogenation catalyzed by the dehydratase and dehydrogenase activities of D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase bifunctional protein (DBP) and enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase bifunctional protein (LBP) in the side chain degradation step of bile acid biosynthesis were investigated using chemically synthesized C27-bile acid CoA esters as substrates. The hydration catalyzed by DBP showed high diastereoselectivity for (24E)-3alpha,7alpha,12alpha-trihydroxy- and (24E)-3alpha,7alpha-dihydroxy-5beta-cholest-24-en-26-oyl CoA to give (24R,25R)-3alpha,7alpha,12alpha,24-tetrahydroxy- and (24R,25R)-3alpha,7alpha,24-trihydroxy-5beta-cholestan-26-oyl CoAs, respectively, and the dehydrogenation catalyzed by DBP also showed high stereospecificity for the above (24R,25R)-isomers to give 3alpha,7alpha,12alpha-trihydroxy- and 3alpha,7alpha-dihydroxy-24-oxo-5beta-cholestan-26-oyl CoAs, respectively. On the other hand, the dehydratase activity of LBP displayed a different diastereoselectivity producing the (24S,25S)-isomer, and dehydrogenase activity of LBP was stereospecific for the (24S,25R)-isomer to give the above 24-oxo-derivative. The hydration and dehydrogenation reactions catalyzed by DBP were effectively conjugated to convert (24E)-5beta-cholestenoyl CoA to 24-oxo-5beta-cholestanoyl CoA. However, the reactions catalyzed by LBP were not conjugated. These results indicate that DBP plays an important role in the biosynthesis of bile acid.
authors.affiliation: Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, 061-0293, Hokkaido, Japan. kurohsuh@hucc.hokudai.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Kurosawa
authors.forename: M
authors.initials: M
authors.lastname: Sato
authors.forename: H
authors.initials: H
authors.lastname: Nakano
authors.forename: M
authors.initials: M
authors.lastname: Fujiwara
authors.forename: T
authors.initials: T
authors.lastname: Murai
authors.forename: T
authors.initials: T
authors.lastname: Yoshimura
authors.forename: T
authors.initials: T
authors.lastname: Hashimoto
mesh_terms: D015067:17-Hydroxysteroid Dehydrogenases; D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism*; D001647:Bile Acids and Salts / Q000096:biosynthesis*; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D004746:Enoyl-CoA Hydratase; D006836:Hydro-Lyases / Q000378:metabolism*; D063991:Mitochondrial Trifunctional Protein; D009097:Multienzyme Complexes / Q000378:metabolism*; D010084:Oxidation-Reduction; D064029:Peroxisomal Multifunctional Protein-2
chemical_list: D001647:Bile Acids and Salts; D009097:Multienzyme Complexes; D015067:17-Hydroxysteroid Dehydrogenases; D015094:3-Hydroxyacyl CoA Dehydrogenases; D063991:Mitochondrial Trifunctional Protein; D006836:Hydro-Lyases; D064029:Peroxisomal Multifunctional Protein-2; C104587:HSD17B4 protein, human; D004746:Enoyl-CoA Hydratase