Su J, Chai X, Kahn B, Napoli J L
Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York 14214, USA.
J Biol Chem. 1998 Jul 10;273(28):17910-6. doi: 10.1074/jbc.273.28.17910.
We report here a mouse cDNA that encodes a 316-amino acid short-chain dehydrogenase that prefers NAD+ as its cofactor and recognizes as substrates androgens and retinols, i.e. has steroid 3alpha- and 17beta-dehydrogenase and cis/trans-retinol catalytic activities. This cis-retinol/androgen dehydrogenase type 2 (CRAD2) shares close amino acid similarity with mouse retinol dehydrogenase isozyme types 1 and 2 and CRAD1 (86, 84, and 87%, respectively). CRAD2 exhibits cooperative kinetics with 3alpha-adiol (3alpha-hydroxysteroid dehydrogenase activity) and testosterone (17beta-hydroxysteroid dehydrogenase activity), but Michaelis-Menten kinetics with androsterone (3alpha-hydroxysteroid dehydrogenase activity), 11-cis-retinol, all-trans-retinol, and 9-cis-retinol, with V/K0.5 values of 1.6, 0.2, 0.1, 0.04, 0.005, and not saturated, respectively. Carbenoxolone (IC50 = 2 microM) and 4-methylpyrazole (IC50 = 5 mM) inhibited CRAD2, but neither ethanol nor phosphatidylcholine had marked effects on its activity. Liver expressed CRAD2 mRNA intensely, with expression in lung, eye, kidney, and brain (2.9, 2, 1.6, and 0.6% of liver mRNA, respectively). CRAD2 represents the fifth isozyme in a group of short-chain dehydrogenase/reductase isozymes (retinol dehydrogenases 1-3 and CRAD1), closely related in primary amino acid sequence (approximately 85%), that are expressed in different quantities in various tissues, have different substrate specificities, and may serve different physiological functions. CRAD2 may alter the amounts of active and inactive androgens and/or convert retinols into retinals. These data expand insight into the multifunctional nature of short-chain dehydrogenases/reductases and into the enzymology of steroid and retinoid metabolism.
我们在此报告一种小鼠cDNA，它编码一种316个氨基酸的短链脱氢酶，该酶更倾向于以NAD⁺作为其辅因子，并识别雄激素和视黄醇作为底物，即具有类固醇3α-和17β-脱氢酶以及顺式/反式视黄醇催化活性。这种2型顺式视黄醇/雄激素脱氢酶（CRAD2）与小鼠视黄醇脱氢酶同工酶1型和2型以及CRAD1具有密切的氨基酸相似性（分别为86%、84%和87%）。CRAD2与3α-二醇（3α-羟基类固醇脱氢酶活性）和睾酮（17β-羟基类固醇脱氢酶活性）表现出协同动力学，但与雄甾酮（3α-羟基类固醇脱氢酶活性）、11-顺式视黄醇、全反式视黄醇和9-顺式视黄醇表现出米氏动力学，其V/K0.5值分别为1.6、0.2、0.1、0.04、0.005且不饱和。生胃酮（IC50 = 2 μM）和4-甲基吡唑（IC50 = 5 mM）抑制CRAD2，但乙醇和磷脂酰胆碱对其活性均无显著影响。肝脏强烈表达CRAD2 mRNA，在肺、眼、肾和脑也有表达（分别为肝脏mRNA的2.9%、2%、1.6%和0.6%）。CRAD2代表短链脱氢酶/还原酶同工酶组中的第五种同工酶（视黄醇脱氢酶1 - 3和CRAD1），它们在一级氨基酸序列上密切相关（约85%），在各种组织中表达量不同，具有不同的底物特异性，可能发挥不同的生理功能。CRAD2可能会改变活性和非活性雄激素的量和/或将视黄醇转化为视黄醛。这些数据扩展了对短链脱氢酶/还原酶多功能性质以及类固醇和类维生素A代谢酶学的认识。
