Characterization of hamster NAD<sup>+</sup>-dependent 3(17)β-hydroxysteroid dehydrogenase belonging to the aldo-keto reductase 1C subfamily
作者:Satoshi Endo、Misato Noda、Akira Ikari、Kenjiro Tatematsu、Ossama El-Kabbani、Akira Hara、Yukio Kitade、Toshiyuki Matsunaga
DOI:10.1093/jb/mvv057
日期:2015.11
The cDNAs for morphine 6-dehydrogenase (AKR1C34) and its homologous aldo-keto reductase (AKR1C35) were cloned from golden hamster liver, and their enzymatic properties and tissue distribution were compared. AKR1C34 and AKR1C35 similarly oxidized various xenobiotic alicyclic alcohols using NAD+, but differed in their substrate specificity for hydroxysteroids and inhibitor sensitivity. While AKR1C34 showed 3α/17β/20α-hydroxysteroid dehydrogenase activities, AKR1C35 efficiently oxidized various 3β- and 17β-hydroxysteroids, including biologically active 3β-hydroxy-5α/β-dihydro-C19/C21-steroids, dehydroepiandrosterone and 17β-estradiol. AKR1C35 also differed from AKR1C34 in its high sensitivity to flavonoids, which inhibited competitively with respect to 17β-estradiol (Ki 0.11–0.69 μM). The mRNA for AKR1C35 was expressed liver-specific in male hamsters and ubiquitously in female hamsters, whereas the expression of the mRNA for AKR1C34 displayed opposite sexual dimorphism. Because AKR1C35 is the first 3(17)β-hydroxysteroid dehydrogenase in the AKR superfamily, we also investigated the molecular determinants for the 3β-hydroxysteroid dehydrogenase activity by replacement of Val54 and Cys310 in AKR1C35 with the corresponding residues in AKR1C34, Ala and Phe, respectively. The mutation of Val54Ala, but not Cys310Phe, significantly impaired this activity, suggesting that Val54 plays a critical role in recognition of the steroidal substrate.
从金黄地鼠肝脏中克隆了羟基脱氢酶(AKR1C34)及其同源醛酮还原酶(AKR1C35)的 cDNA,并比较了它们的酶学性质和组织分布。AKR1C34 和 AKR1C35 均能利用 NAD+ 氧化各种外源性的脂环醇,但在羟基类固醇的底物特异性和抑制剂敏感性方面有所不同。AKR1C34 显示出 3α/17β/20α-羟基类固醇脱氢酶活性,而 AKR1C35 能有效氧化多种 3β-和 17β-羟基类固醇,包括具有生物活性的 3β-羟基-5α/β-二氢C19/C21-类固醇、脱氢表雄酮和 17β-雌二醇。AKR1C35 在黄酮类化合物的高敏感性方面也与 AKR1C34 不同,黄酮类化合物以竞争方式抑制 17β-雌二醇(Ki 0.11–0.69 μM)。AKR1C35 的 mRNA 在雄性地鼠中肝脏特异性表达,而在雌性地鼠中普遍表达,AKR1C34 的 mRNA 表达则显示出相反的性二态性。由于 AKR1C35 是 AKR 超家族中第一个 3(17)β-羟基类固醇脱氢酶,我们还通过将 AKR1C35 中的 Val54 和 Cys310 替换为 AKR1C34 中的相应残基 Ala 和 Phe,研究了 3β-羟基类固醇脱氢酶活性的分子决定因素。Val54Ala 突变显著损害了这一活性,而 Cys310Phe 突变则没有,这表明 Val54 在识别甾体底物中起着关键作用。