title: Enzymatic properties of a member (AKR1C20) of the aldo-keto reductase family.
abstract: AKR1C20, a member of the aldo-keto reductase (AKR) superfamily, found by mouse genomic analysis, exhibits the highest sequence identity (89%) with mouse liver 17beta-hydroxysteroid dehydrogenase (HSD) type 5, but its function remains unknown. In this report, we have expressed the recombinant AKR1C20 from its cDNA, and examined its properties. The purified enzyme was a 36-kDa monomer, and showed both 17beta-HSD and 3alpha-HSD activities in the presence of NADP(H) as the coenzymes. While the Km values for testosterone and 5alpha-dihydrotestosterone were high (>0.2 mM), those for 3alpha-hydroxy- and 3-keto-steroids were low (0.3-5 microM), resulting in high catalytic efficiency for the substrates. Although no significant dehydrogenase activity towards non-steroidal alcohols was observed, the enzyme highly reduced alpha-dicarbonyl compounds such as 16-ketoestrone, 9,10-phenanthrenequinone, acenaphthenequinone, 1-phenylisatin and camphorquinone. The pH optima of the dehydrogenase and reductase activities were 10.5 and 6.5-7.5, respectively. The enzyme was inhibited by sulfobromophthalein, hexestrol, indomethacin and flufenamic acid. The properties of AKR1C20 are distinct from those of previously known mouse 17beta-HSD type 5 (AKR1C6), 3alpha-HSD (AKR1C14) and other members of the AKR1C subfamily. Thus, AKR1C20 is a novel 3alpha(17beta)-HSD, which may also function as a reductase for xenobiotic alpha-dicarbonyl compounds.
authors.affiliation: Laboratory of Biochemistry, Gifu Pharmaceutical University, Mitahora-higashi, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Endo
authors.forename: Shuhei
authors.initials: S
authors.lastname: Ishikura
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 / Q000302:isolation & purification / Q000378:metabolism; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific) / Q000235:genetics / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000235:genetics* / Q000378:metabolism*; D000449:Aldehyde Reductase; D000074408:Aldo-Keto Reductases; D000818:Animals; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D006914:Hydroxysteroids / Q000378:metabolism; D007664:Ketosteroids / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D051379:Mice; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D018076:DNA, Complementary; D006914:Hydroxysteroids; D007664:Ketosteroids; D012333:RNA, Messenger; D011994:Recombinant Proteins; D015067:17-Hydroxysteroid Dehydrogenases; D000429:Alcohol Oxidoreductases; D000074408:Aldo-Keto Reductases; D000449:Aldehyde Reductase; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); C000614209:AKR7A5 protein, mouse