title: Molecular cloning of a novel type of rat cytoplasmic 17beta-hydroxysteroid dehydrogenase distinct from the type 5 isozyme.
abstract: Rat liver contains two cytosolic enzymes (TBER1 and TBER2) that reduce 6-tert-butyl-2,3-epoxy-5-cyclohexene-1,4-dione into its 4R- and 4S-hydroxy metabolites. In this study, we cloned the cDNA for TBER1 and examined endogenous substrates using the homogenous recombinant enzyme. The cDNA encoded a protein composed of 323 amino acids belonging to the aldo-keto reductase family. The recombinant TBER1 efficiently oxidized 17beta-hydroxysteroids and xenobiotic alicyclic alcohols using NAD+ as the preferred coenzyme at pH 7.4, and showed low activity towards 20alpha- and 3alpha-hydroxysteroids, and 9-hydroxyprostaglandins. The enzyme was potently inhibited by diethylstilbestrol, hexestrol and zearalenone. The coenzyme specificity, broad substrate specificity and inhibitor sensitivity of the enzyme differed from those of rat NADPH-dependent 17beta-hydroxysteroid dehydrogenase type 5, which was cloned from the liver and characterized using the recombinant enzyme. The mRNA for TBER1 was highly expressed in rat liver, gastrointestinal tract and ovary, in contrast to specific expression of 17beta-hydroxysteroid dehydrogenase type 5 mRNA in the liver and kidney. Thus, TBER1 represents a novel type of 17beta-hydroxysteroid dehydrogenase with unique catalytic properties and tissue distribution. In addition, TBER2 was identified as 3alpha-hydroxysteroid dehydrogenase on chromatographic analysis of the enzyme activities in rat liver cytosol and characterization of the recombinant 3alpha-hydroxysteroid dehydrogenase.
authors.affiliation: Laboratory of Biochemistry, Gifu Pharmaceutical University, Gifu 502-8585.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Ishikura
authors.forename: Kengo
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Masaharu
authors.initials: M
authors.lastname: Sanai
authors.forename: Kenji
authors.initials: K
authors.lastname: Horie
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Matsunaga
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tajima
authors.forename: Ossama
authors.initials: O
authors.lastname: El-Kabbani
authors.forename: Akira
authors.initials: A
authors.lastname: Hara
mesh_terms: D015067:17-Hydroxysteroid Dehydrogenases / Q000235:genetics* / Q000378:metabolism; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000201:enzymology*; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007668:Kidney / Q000201:enzymology / Q000378:metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010053:Ovary / Q000201:enzymology / Q000378:metabolism; D010084:Oxidation-Reduction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013270:Stomach / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D007527:Isoenzymes; D012333:RNA, Messenger; D011994:Recombinant Proteins; D015067:17-Hydroxysteroid Dehydrogenases; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase