植物雌激素是在功能上和结构上模拟哺乳动物雌激素的植物衍生化合物。植物雌激素对几种类固醇生成酶具有广泛的抑制活性,如17β-羟基类固醇脱氢酶(17β-HSDs),调节哺乳动物中雄激素和雌激素的生物学效力。然而,到目前为止,没有晶体学数据可以解释植物雌激素与哺乳动物17β-HSD的结合。来自丝状真菌Cochlioboluslunatus(17β-HSDcl)的NADP(H)依赖性17β-HSD一直是广泛的生化研究的主题,动力学和定量结构-活性关系研究表明,黄酮醇是最有效的抑制剂。在本研究中,我们研究了17β-HSDcl的holo形式与山奈酚和3,7-二羟基黄酮之间的三元复合物的构效关系,与异黄酮染料木素和biochaninA相比,晶体学数据伴随着对六种黄酮醇的抑制机制的动力学分析(3-羟基黄酮,3,7-二羟基黄酮,山奈酚,槲皮素,Fisetin,杨梅素),一种黄烷酮(柚皮素),一黄酮(木犀草素),和两种异黄酮(染料木素,biochaninA)。动力学分析表明,环B的羟基化程度显著影响黄酮醇的总体抑制效力。不同的结合模式定义了17β-HSDcl与黄酮和异黄酮之间的相互作用。此外,与biochaninA的复合物揭示了一种异常的结合模式,该模式似乎解释了其对金雀异黄素对17β-HSDcl的更大抑制作用。总的来说,这些数据为鉴定支持植物雌激素抑制17β-HSD的不同分子决定子提供了蓝图。
Phytoestrogens are plant-derived compounds that functionally and structurally mimic mammalian estrogens. Phytoestrogens have broad inhibitory activities toward several steroidogenic enzymes, such as the 17β-hydroxysteroid dehydrogenases (17β-HSDs), which modulate the biological potency of androgens and estrogens in mammals. However, to date, no crystallographic data are available to explain phytoestrogens binding to mammalian 17β-HSDs. NADP(H)-dependent 17β-HSD from the filamentous fungus Cochliobolus lunatus (17β-HSDcl) has been the subject of extensive biochemical, kinetic and quantitative structure-activity relationship studies that have shown that the flavonols are the most potent inhibitors. In the present study, we investigated the structure-activity relationships of the ternary complexes between the holo form of 17β-HSDcl and the flavonols kaempferol and 3,7-dihydroxyflavone, in comparison with the isoflavones genistein and biochanin A. Crystallographic data are accompanied by kinetic analysis of the inhibition mechanisms for six flavonols (3-hydroxyflavone, 3,7-dihydroxyflavone, kaempferol, quercetin, fisetin, myricetin), one flavanone (naringenin), one flavone (luteolin), and two isoflavones (genistein, biochanin A). The kinetics analysis shows that the degree of hydroxylation of ring B significantly influences the overall inhibitory efficacy of the flavonols. A distinct binding mode defines the interactions between 17β-HSDcl and the flavones and isoflavones. Moreover, the complex with biochanin A reveals an unusual binding mode that appears to account for its greater inhibition of 17β-HSDcl with respect to genistein. Overall, these data provide a blueprint for identification of the distinct molecular determinants that underpin 17β-HSD inhibition by phytoestrogens.