Human cytosolic 3α-hydroxysteroid dehydrogenases of the aldo-keto reductase superfamily display significant 3β-hydroxysteroid dehydrogenase activity -: Implications for steroid hormone metabolism and action
Human cytosolic 3α-hydroxysteroid dehydrogenases of the aldo-keto reductase superfamily display significant 3β-hydroxysteroid dehydrogenase activity -: Implications for steroid hormone metabolism and action
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DOI：
10.1074/jbc.m313308200
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发表时间：
2004-03-12
影响因子：
4.8
通讯作者：
Penning, TM
中科院分区：
文献类型：
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作者：
Steckelbroeck, S;Jin, Y;Penning, TM
依赖NADPH的胞浆3β-羟基类固醇脱氢酶(3β-HSD)活性的来源尚不清楚。例如，这一重要的反应导致有效的雄激素5α-二氢睾酮(DHT)被还原为无活性的3β-雄烷二醇(3β-Diol)。四种人类胞质醛酮还原酶(AKR1C1AKR1C4)是已知的非位置特异性3α/17beta/20pha-HSD。我们现在证明了AKR1Cs催化DHT还原为3α-和3β-二醇(通过H-1核磁共振谱建立)。3α-二醇和3β-二醇的生成率在不同的异构体之间差异很大，但对于每种酶，这两种活性都同样被非类固醇抗炎药物氟苯那酸抑制。在体外，以3α-二醇为底物，AKR1Cs也表达了大量的3α[17β]-羟基类固醇氧化酶活性。然而，与酶的3-酮类固醇还原酶活性相反，它们的羟基类固醇氧化酶活性被相对低摩尔浓度的相反辅因子(NADPH)有效地抑制。这表明在体内，所有的AKR1C都将优先作为还原酶发挥作用。人肝癌(HepG2)细胞(缺乏3β-HSD/Delta(5-4)酮类固醇异构酶mRNA表达，但表达AKR1C1-AKR1C3)能够将DHT转化为3α和3β-Diol。这种转化被氟苯那酸抑制，证实了AKR1C酶的3α/3β-HSD活性在体内的意义。利用AKR1C1和AKR1C2的现有晶体结构进行的分子对接模拟展示了3pha/3beta-HSD活性是如何实现的。观察到AKR1Cs是3β-四氢类固醇的来源具有生理意义，因为：(1)3-β-二醇(相对于3-α-二醇)的形成几乎是不可逆的；(2)3-二醇是雌激素受体β的促凋亡配基；(3)3-β-四氢类固醇是γ-氨基丁酸A受体拮抗剂。
The source of NADPH-dependent cytosolic 3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity is unknown to date. This important reaction leads e. g. to the reduction of the potent androgen 5alpha-dihydrotestosterone (DHT) into inactive 3beta-androstanediol (3beta-Diol). Four human cytosolic aldo-keto reductases (AKR1C1 AKR1C4) are known to act as non-positional-specific 3alpha- / 17beta- /20alpha-HSDs. We now demonstrate that AKR1Cs catalyze the reduction of DHT into both 3alpha- and 3beta-Diol ( established by H-1 NMR spectroscopy). The rates of 3alpha-versus 3beta-Diol formation varied significantly among the isoforms, but with each enzyme both activities were equally inhibited by the nonsteroidal anti-inflammatory drug flufenamic acid. In vitro, AKR1Cs also expressed substantial 3alpha[17beta]-hydroxysteroid oxidase activity with 3alpha-Diol as the substrate. However, in contrast to the 3-ketosteroid reductase activity of the enzymes, their hydroxysteroid oxidase activity was potently inhibited by low micromolar concentrations of the opposing cofactor ( NADPH). This indicates that in vivo all AKR1Cs will preferentially work as reductases. Human hepatoma (HepG2) cells (which lack 3beta-HSD/Delta(5-4) ketosteroid isomerase mRNA expression, but express AKR1C1 - AKR1C3) were able to convert DHT into 3alpha- and 3beta-Diol. This conversion was inhibited by flufenamic acid establishing the in vivo significance of the 3alpha/ 3beta-HSD activities of the AKR1C enzymes. Molecular docking simulations using available crystal structures of AKR1C1 and AKR1C2 demonstrated how 3alpha/3beta-HSD activities are achieved. The observation that AKR1Cs are a source of 3beta-tetrahydrosteroids is of physiological significance because: (i) the formation of 3beta-Diol ( in contrast to 3alpha-Diol) is virtually irreversible, (ii) 3beta-Diol is a pro-apoptotic ligand for estrogen receptor beta, and (iii) 3beta-tetrahydrosteroids act as gamma-aminobutyric acid type A receptor antagonists.