title: Characterization of a human 20alpha-hydroxysteroid dehydrogenase.
abstract: It has been suggested that 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) is a T-cell differentiation marker in mice. In the human, this enzyme has generally been associated with types 1 and 2 17beta-HSDs, which belong to the short-chain alcohol dehydrogenase family, whereas the rat, rabbit, pig and bovine 20alpha-HSDs are members of the aldoketo reductase superfamily, which also includes the 3alpha-HSD family. In this study, we report the cloning, from a human skin cDNA library, of a cDNA that shows, after transfection into human embryonic kidney (HEK-293) cells, high 20alpha-HSD activity but negligible 3alpha- and 17beta-hydroxysteroid dehydrogenase activities. A comparison of the amino acid sequence of the human 20alpha-HSD with those of other related 20alpha- and 3alpha-HSDs indicates that the human 20alpha-HSD shares 79.9, 68.7 and 52.3% identity with rabbit, rat and bovine 20alpha-HSDs, whereas it shows 97, 84 and 65% identity with human type 3, type 1 and rat 3alpha-HSDs. In contrast, the enzyme shares only 15.2 and 15.0% identity with type 1 and type 2 human 17beta-HSDs. DNA analysis predicts a protein of 323 amino acids, with a calculated molecular weight of 36 767 Da. In intact transfected cells, the human 20alpha-HSD preferentially catalyzes the reduction of progesterone to 20alpha-hydroxyprogesterone with a K(m) value of 0.6 microM, the reverse reaction (oxidation) being negligible. In a cell cytosolic preparation, the enzyme could use both NADPH and NADH as cofactors, but NADPH, which gave 4-fold lower K(m) values, was preferred. We detected the expression of 20alpha-HSD mRNA in liver, prostate, testis, adrenal, brain, uterus and mammary-gland tissues and in human keratinocyte (HaCaT) cells. The present study clearly indicates that the genuine human 20alpha-HSD belongs to the aldoketo reductase family, like the 20alpha-HSDs from other species.
authors.affiliation: Oncology and Molecular Endocrinology Research Center, CHUQ PCHUL and Laval University, Quebec, Quebec G1V 4G2, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: I
authors.initials: I
authors.lastname: Dufort
authors.forename: P
authors.initials: P
authors.lastname: Rheault
authors.forename: V
authors.initials: V
authors.lastname: Luu-The
mesh_terms: D015089:20-Hydroxysteroid Dehydrogenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D043607:20-alpha-Hydroxysteroid Dehydrogenase; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002460:Cell Line; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009249:NADP / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014162:Transfection
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D009249:NADP; D015089:20-Hydroxysteroid Dehydrogenases; D043607:20-alpha-Hydroxysteroid Dehydrogenase