Structure and activity of the murine type 5 17beta-hydroxysteroid dehydrogenase gene(1).
17beta-Hydroxysteroid dehydrogenases (17beta-HSDs) play a crucial role in the control of active sex steroid intracellular levels. Seven types of 17beta-HSD have been described. In this study, we report the cloning and characterization of the mouse type 5 17beta-HSD belonging to the aldo-keto reductase superfamily, in contrast with types 1, 2, 3, 4, 6, and 7 17beta-HSD which belong to the short-chain alcohol dehydrogenase family. The gene spans 16 kb and contains 9 exons separated by 8 introns. Primer extension analysis identified a major transcription start site beginning 50 nucleotides upstream from the ATG initiation codon. Northern blot analysis showed a high mRNA expression level in the liver and a weaker signal in the kidney. To determine more precisely the substrate specificity of the enzyme, we established a stable cell line expressing mouse type 5 17beta-HSD in transformed human embryonic kidney (293) cells. The transfected cell line preferentially catalyzes the transformation of 4-androstenedione (4-dione) and androstanedione (A-dione) into testosterone (T) and dihydrotestosterone (DHT), respectively. This data is somewhat in contradiction with a previous study that described the enzyme as estradiol 17beta-dehydrogenase. Our results indicate that the rate of transformation of estradiol (E(2)) to estrone (E(1)) represents only 1% of the rate of transformation of 4-dione to T. Mouse type 5 17beta-HSD shares 76% amino acid sequence identity with human type 5 17beta-HSD; 71%, 76%, 76% with rat 3alpha-HSD and human types 1 and 3 3alpha-HSDs, respectively; and 71%, 69% and 77% with mouse, rat and human 20alpha-HSD, respectively.
Rheault
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Medical Research Council Group in Molecular Endocrinology, CHUL Research Center and Laval University, 2705 Laurier Boulevard, Quebec, PQ, Canada.
Charbonneau
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D015067:17-Hydroxysteroid Dehydrogenases / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D000735:Androstenedione / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000302:isolation & purification; D013196:Dihydrotestosterone / Q000378:metabolism; D005043:Etiocholanolone / Q000378:metabolism; D005786:Gene Expression Regulation; D051379:Mice; D008969:Molecular Sequence Data; D015183:Restriction Mapping; D013379:Substrate Specificity; D013739:Testosterone / Q000378:metabolism
D018076:DNA, Complementary; D013196:Dihydrotestosterone; D013739:Testosterone; D000735:Androstenedione; D005043:Etiocholanolone; D015067:17-Hydroxysteroid Dehydrogenases