Zhang Y, Dufort I, Rheault P, Luu-The V
Oncology and Molecular Endocrinology Research Center, CHUQ PCHUL and Laval University, Quebec, Quebec G1V 4G2, Canada.
J Mol Endocrinol. 2000 Oct;25(2):221-8. doi: 10.1677/jme.0.0250221.
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.
有人提出，20α-羟基类固醇脱氢酶（20α-HSD）是小鼠T细胞分化标志物。在人类中，这种酶通常与1型和2型17β-羟基类固醇脱氢酶相关，它们属于短链醇脱氢酶家族，而大鼠、兔、猪和牛的20α-HSD是醛酮还原酶超家族的成员，该超家族还包括3α-HSD家族。在本研究中，我们报道了从人皮肤cDNA文库中克隆出一个cDNA，该cDNA转染到人胚肾（HEK-293）细胞后显示出高20α-HSD活性，但3α-和17β-羟基类固醇脱氢酶活性可忽略不计。将人20α-HSD的氨基酸序列与其他相关的20α-和3α-HSD的氨基酸序列进行比较表明，人20α-HSD与兔、大鼠和牛的20α-HSD的同一性分别为79.9%、68.7%和52.3%；而与人3型、1型和大鼠3α-HSD的同一性分别为97%、84%和65%。相比之下，该酶与人1型和2型17β-羟基类固醇脱氢酶的同一性仅为15.2%和15.0%。DNA分析预测该蛋白由323个氨基酸组成，计算分子量为36 767 Da。在完整的转染细胞中，人20α-HSD优先催化孕酮还原为20α-羟基孕酮，K(m)值为0.6 μM，逆反应（氧化）可忽略不计。在细胞胞质制备物中，该酶可以使用NADPH和NADH作为辅因子，但优先选择NADPH，其K(m)值低4倍。我们在肝脏、前列腺、睾丸、肾上腺、脑、子宫和乳腺组织以及人角质形成细胞（HaCaT）中检测到了20α-HSD mRNA的表达。本研究清楚地表明，真正的人20α-HSD与其他物种的20α-HSD一样，属于醛酮还原酶家族。
