Pelletier G, Dupont E, Simard J, Luu-The V, Bélanger A, Labrie F
MRC Group in Molecular Endocrinology, CHUL Research Center, Quebec, Canada.
J Steroid Biochem Mol Biol. 1992 Oct;43(5):451-67. doi: 10.1016/0960-0760(92)90084-v.
Primates are unique in having adrenals that secrete large amounts of the precursor sex steroids (PSS) dehydroepiandrosterone (DHEA) and especially DHEA-sulfate. The adrenal PSS require the action of 3 beta-hydroxysteroid dehydrogenase/5-ene-4 ene isomerase (3 beta-HSD), 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD), 5 alpha-reductase and/or aromatase to form the androgen dihydrotestosterone (DHT) or the estrogens 17 beta-estradiol and androst-5-ene-diol. Knowing the crucial role of 3 beta-HSD and 17 beta-HSD in sex steroid biosynthesis both in classical as well as in peripheral steroidogenic tissues, we have concentrated our efforts on the elucidation of the molecular structure of these enzyme families. We have thus characterized two types of human 3 beta-HSD cDNA clones and their corresponding genes which encode deduced proteins of 371 and 372 amino acids and share 93.5% homology. Human type I 3 beta-HSD is the almost exclusive mRNA species expressed in the placenta and skin, while human type II is the predominant mRNA species in the adrenals, ovaries and testes. We have also recently elucidated the structure of three types of rat 3 beta-HSD cDNAs which all encode a 372 amino acid protein. The predicted rat type I and II 3 beta-HSD proteins expressed adrenals, gonads and adipose tissue share 94% homology while they share 80% similarity with the liver-specific type III 3 beta-HSD. Transient expression of human type I and II as well as rat type I and II 3 beta-HSD cDNAs in HeLa human cervical carcinoma cells reveals that 3 beta-ol dehydrogenase and 5-ene-4-ene isomerase activities reside within a single protein and that these cDNAs encode functional 3 beta-HSD proteins. The expressed rat type III protein possesses a unique property catalyzing selectively the reduction of 3 beta-androstane 5 alpha-steroids such as DHT. Furthermore, we have also demonstrated by site-directed mutagenesis that the lower activity of expressed rat type II compared to rat type I 3 beta-HSD protein is due to a change of four amino acid residues potentially involved in a membrane-spanning domain. In parallel, we have characterized the complete nucleotide sequence of human 17 beta-HSD cDNA clones encoding a 327 amino acid protein as well as two in tandem 17 beta-HSD genes. Two major 17 beta-HSD mRNA species have been detected in several tissues due to a tissue-specific alternative site of initiation of transcription.(ABSTRACT TRUNCATED AT 400 WORDS)
灵长类动物的独特之处在于其肾上腺能分泌大量的前体性类固醇（PSS）脱氢表雄酮（DHEA），尤其是硫酸脱氢表雄酮。肾上腺PSS需要3β-羟基类固醇脱氢酶/5-烯-4-烯异构酶（3β-HSD）、17β-羟基类固醇脱氢酶（17β-HSD）、5α-还原酶和/或芳香化酶的作用才能形成雄激素双氢睾酮（DHT）或雌激素17β-雌二醇和雄甾-5-烯二醇。鉴于3β-HSD和17β-HSD在经典及外周类固醇生成组织的性类固醇生物合成中起着关键作用，我们致力于阐明这些酶家族的分子结构。因此，我们鉴定了两种类型的人类3β-HSD cDNA克隆及其相应基因，它们编码由371和372个氨基酸组成的推导蛋白，同源性为93.5%。人类I型3β-HSD几乎是胎盘和皮肤中唯一表达的mRNA种类，而人类II型是肾上腺、卵巢和睾丸中的主要mRNA种类。我们最近还阐明了三种类型的大鼠3β-HSD cDNA的结构，它们均编码一个由372个氨基酸组成的蛋白。预测的大鼠I型和II型3β-HSD蛋白在肾上腺、性腺和脂肪组织中表达，同源性为94%，而它们与肝脏特异性III型3β-HSD的相似性为80%。人类I型和II型以及大鼠I型和II型3β-HSD cDNA在HeLa人宫颈癌细胞中的瞬时表达表明，3β-醇脱氢酶和5-烯-4-烯异构酶活性存在于单一蛋白中，且这些cDNA编码功能性3β-HSD蛋白。所表达的大鼠III型蛋白具有独特的特性，能选择性催化3β-雄烷5α-类固醇如DHT的还原。此外，我们还通过定点诱变证明，所表达的大鼠II型3β-HSD蛋白与大鼠I型相比活性较低是由于可能参与跨膜结构域的四个氨基酸残基发生了变化。同时，我们鉴定了编码一个由327个氨基酸组成蛋白的人类17β-HSD cDNA克隆的完整核苷酸序列以及两个串联的17β-HSD基因。由于转录起始位点的组织特异性选择，在多个组织中检测到了两种主要的17β-HSD mRNA种类。（摘要截短于400字）
