Kazeto Yukinori, Ijiri Shigeho, Matsubara Hajime, Adachi Shinji, Yamauchi Kohei
Division of Marine Biosciences, Graduate School of Fisheries Science, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido 041-8611, Japan.
J Steroid Biochem Mol Biol. 2003 May;85(1):49-56. doi: 10.1016/s0960-0760(03)00138-9.
3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase (3beta-HSD) is a crucial steroidogenic enzyme which catalyzes an essential step in the biosynthesis of all classes of steroid hormones. Two closely related cDNAs, encoding Japanese eel ovarian types I and II 3beta-HSD, were cloned and characterized. Both cDNAs putatively encoded 375 amino acid residues sharing high sequence homology with those of rainbow trout (71%) and mammalian (approximately 45-50%) 3beta-HSD. Transient expression of types I and II 3beta-HSD in COS-7 cells revealed that both proteins possess 3beta-hydroxysteroid dehydrogenase as well as Delta(5)-Delta(4) isomerase activity for both pregnenolone and dehydroepiandrosterone, with the preference of pregnenolone over dehydroepiandrosterone as substrate, although the type I protein is more active than the type II. By northern blot analysis, a single band of the 3beta-HSD transcript of approximately 1.5kb in length was observed in ovarian tissue and the total transcript abundance of both 3beta-HSDs remained constant throughout ovarian development artificially induced by gonadotropin-rich salmon pituitary homogenate. This lack of change in 3beta-HSD transcript abundance during ovarian development did not correlate with the fluctuation of its enzymatic activity reported previously, which may suggest that changes in 3beta-HSD activity during ovarian development may be, in part, post-transcriptionally regulated in the Japanese eel ovary.
3β-羟基类固醇脱氢酶/Δ⁵-Δ⁴异构酶（3β-HSD）是一种关键的类固醇生成酶，它催化所有类型类固醇激素生物合成中的一个关键步骤。克隆并鉴定了两个密切相关的cDNA，它们编码日本鳗鲡卵巢I型和II型3β-HSD。这两个cDNA推定编码375个氨基酸残基，与虹鳟鱼（71%）和哺乳动物（约45 - 50%）的3β-HSD具有高度序列同源性。I型和II型3β-HSD在COS-7细胞中的瞬时表达表明，这两种蛋白质对孕烯醇酮和脱氢表雄酮都具有3β-羟基类固醇脱氢酶以及Δ⁵-Δ⁴异构酶活性，尽管I型蛋白质比II型更具活性，但它们更倾向于以孕烯醇酮而非脱氢表雄酮作为底物。通过Northern印迹分析，在卵巢组织中观察到一条长度约为1.5kb的3β-HSD转录本单带，并且在富含促性腺激素的鲑鱼垂体匀浆人工诱导的整个卵巢发育过程中，两种3β-HSD的总转录本丰度保持恒定。卵巢发育过程中3β-HSD转录本丰度的这种缺乏变化与先前报道的其酶活性波动不相关，这可能表明日本鳗鲡卵巢中3β-HSD活性在卵巢发育过程中的变化可能部分受到转录后调控。
