Complementary deoxyribonucleic acid cloning and enzymatic characterization of a novel 17beta/3alpha-hydroxysteroid/retinoid short chain dehydrogenase/reductase.
17Beta-hydroxysteroid dehydrogenases (17betaHSDs) convert androgens and estrogens between their active and inactive forms, whereas retinol dehydrogenases catalyze the conversion between retinol and retinal. Retinol dehydrogenases function in the visual cycle, in the generation of the hormone retinoic acid, and some also act on androgens. Here we report cloning and expression of a complementary DNA that encodes a new mouse liver microsomal member of the short chain dehydrogenase/reductase (SDR) superfamily and its enzymatic characterization, i.e. 17betaHSD9. Although 17betaHSD9 shares 88% amino acid identity with rat 17betaHSD6, its closest homolog, the two differ in substrate specificity. In contrast to other 17betaHSD, 17betaHSD9 has nearly equivalent activities as a 17betaHSD (with estradiol approximately = adiol) and as a 3alphaHSD (with adiol approximately = androsterone). It also recognizes retinol as substrate and represents in part the NAD+-dependent liver microsomal dehydrogenase that uses unbound retinol, but not retinol complexed with cellular retinol-binding protein. Thus, this enzyme has catalytic properties that overlap with two subgroups of SDR, 17betaHSD and retinol dehydrogenases. Inactivation of estrogen and a variety of androgens seems to be its most probable function. Because of its apparent inability to access retinol bound with cellular retinol-binding protein, a function in the pathway of retinoic acid biosynthesis seems less obvious. These data provide additional insight into the enzymology of estrogen, androgen, and retinoid metabolism and illustrate how closely related members of the SDR superfamily can have strikingly different substrate specificities.
Su
J
J
Department of Biochemistry, State University of New York School of Medicine and Biomedical Sciences, Buffalo 14214, USA.
Lin
M
M
Napoli
J L
JL
D015067:17-Hydroxysteroid Dehydrogenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D000072467:Cytochrome P450 Family 2; D018076:DNA, Complementary / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009243:NAD / Q000494:pharmacology; D009249:NADP / Q000494:pharmacology; D051381:Rats; D013379:Substrate Specificity; D014212:Tretinoin / Q000378:metabolism; D014801:Vitamin A / Q000378:metabolism
D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009243:NAD; D014801:Vitamin A; D004958:Estradiol; D009249:NADP; D014212:Tretinoin; D015067:17-Hydroxysteroid Dehydrogenases; D000429:Alcohol Oxidoreductases; C022520:retinol dehydrogenase; C504568:Cyp2d1 protein, rat; D000072467:Cytochrome P450 Family 2