title: 3-Keto reductase activity of estradiol-17 beta dehydrogenase and its contribution to androgen metabolism.
abstract: Hepatic estradiol-17 beta dehydrogenase from chickens catalyzed the reduction of the 3-keto group of androgens such as 5 alpha-dihydrotestosterone and 5 alpha-androstane-3,17-dione as well as the 17-keto reduction of 4-androstene-3,17-dione and dehydroepiandrosterone. The reaction products from 17-ketosteroid and 3-ketosteroid substrates were identified as 17 beta-hydroxysteroids and 3 beta-hydroxysteroids, respectively, by thin layer chromatography, high performance liquid chromatography and gas chromatography. Barbital inhibited both 17 beta-estradiol dehydrogenase and 5 alpha-androstane-3,17-dione reductase activity noncompetitively giving the same kinetic constant, Ki = 50 microM. 5 alpha-Androstane-3,17-dione competitively inhibited 17 beta-estradiol dehydrogenase activity. These results indicate that chicken liver estradiol-17 beta dehydrogenase is in fact a 3 beta- and 17 beta-hydroxysteroid dehydrogenase and that both 3- and 17-ketosteroids bind to the same catalytic site.
authors.affiliation: Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Osaka University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nishinaka
authors.forename: Y
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: N
authors.initials: N
authors.lastname: Terada
authors.forename: T
authors.initials: T
authors.lastname: Terada
authors.forename: T
authors.initials: T
authors.lastname: Mizoguchi
authors.forename: T
authors.initials: T
authors.lastname: Nishihara
mesh_terms: D000728:Androgens / Q000378:metabolism*; D000818:Animals; D002645:Chickens; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004960:Estradiol Dehydrogenases / Q000302:isolation & purification / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D000728:Androgens; D004960:Estradiol Dehydrogenases