Andersson S, Russell D W
Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235.
Proc Natl Acad Sci U S A. 1990 May;87(10):3640-4. doi: 10.1073/pnas.87.10.3640.
The microsomal enzyme steroid 5 alpha-reductase is responsible for the conversion of testosterone into the more potent androgen dihydrotestosterone. In man, this steroid acts on a variety of androgen-responsive target tissues to mediate such diverse endocrine processes as male sexual differentiation in the fetus and prostatic growth in men. Here we describe the isolation, structure, and expression of a cDNA encoding the human steroid 5 alpha-reductase. A rat cDNA was used as a hybridization probe to screen a human prostate cDNA library. A 2.1-kilobase cDNA was identified and DNA sequence analysis indicated that the human steroid 5 alpha-reductase was a hydrophobic protein of 259 amino acids with a predicted molecular weight of 29,462. A comparison of the human and rat protein sequences revealed a 60% identity. Transfection of expression vectors containing the human and rat cDNAs into simian COS cells resulted in the synthesis of high levels of steroid 5 alpha-reductase enzyme activity. Both enzymes expressed in COS cells showed similar substrate specificities for naturally occurring steroid hormones. However, synthetic 4-azasteroids demonstrated marked differences in their abilities to inhibit the human and rat steroid 5 alpha-reductases.
微粒体酶类固醇5α-还原酶负责将睾酮转化为活性更强的雄激素双氢睾酮。在人类中，这种类固醇作用于多种雄激素反应性靶组织，以介导诸如胎儿期男性性分化和男性前列腺生长等多种内分泌过程。在此，我们描述了编码人类类固醇5α-还原酶的cDNA的分离、结构和表达。用大鼠cDNA作为杂交探针筛选人类前列腺cDNA文库。鉴定出一个2.1千碱基的cDNA，DNA序列分析表明人类类固醇5α-还原酶是一种由259个氨基酸组成的疏水蛋白，预测分子量为29462。人类和大鼠蛋白质序列的比较显示有60%的同一性。将含有人类和大鼠cDNA的表达载体转染到猴COS细胞中，导致高水平的类固醇5α-还原酶活性的合成。在COS细胞中表达的两种酶对天然存在的类固醇激素表现出相似的底物特异性。然而，合成的4-氮杂类固醇在抑制人类和大鼠类固醇5α-还原酶的能力上表现出显著差异。
