Synthesis and Biochemical Studies of 19-Oxygenated Derivatives of 6.ALPHA.- and 6.BETA.-Methylandrostenediones as Catalytic Probes for the Active Site of Aromatase.
作者:Mitsuteru NUMAZAWA、Akiko YOSHIMURA
DOI:10.1248/bpb.23.1059
日期:——
To gain insight into the binding aspects of 6α- and 6β-methylandrostenediones (1 and 2), potent competitive inhibitors and effective substrates of aromatase, at the active site of the enzyme, we synthesized their 19-hydroxy and 19-oxo derivatives to determine their inhibition of aromatase activity as well as their aromatization rates in human placental microsomes. The 6β- and 6α-methyl-19-ols 12 and 13 were produced from 19-(tert-butyl-dimethylsiloxy)androstenedione (6) in 6 steps in which the Grignard reaction of 5α, 6α-epoxy steroid 8 with CH3MgBr was employed as a key reaction. Oxidation of the 19-ols 12 and 13 yielded the corresponding 19-als 14 and 15. The 6α-methyl steroids 13 and 15 were good competitive inhibitors of aromatase (Ki≤100 nM), and their aromatization rates obtained by gas chromatography-mass spectrometric analysis were 110 and 205pmol/min/mg protein, respectively. In contrast, the 6β-methyl isomers 12 and 14 were non-competitive inhibitors, with Ki values of more than 500 nM, and they were aromatized at rates of 16 and 20 pmol/min/mg protein, respectively. These results reveal that there is a marked difference in binding to the active site between the 19-oxygenated 6α-methyl and 6β-methyl inhibitors where the binding manner of the 6α-steroids, rather than the 6β-isomers, is suitable as a substrate for aromatase.
6α- 和 6β- 甲基雄烯二酮(1 和 2)是芳香化酶的强效竞争性抑制剂和有效底物,为了深入了解它们与芳香化酶活性位点的结合情况,我们合成了它们的 19- 羟基和 19- 氧代衍生物,以确定它们对芳香化酶活性的抑制作用以及它们在人类胎盘微粒体中的芳香化率。6β-和 6α-甲基-19-醇 12 和 13 是由 19-(叔丁基-二甲基硅氧基)雄烯二酮(6)经 6 个步骤合成的,其中 5α、6α-环氧类固醇 8 与 CH3MgBr 的格氏反应被用作关键反应。19- 醇 12 和 13 氧化生成相应的 19-醛 14 和 15。6α- 甲基类固醇 13 和 15 是芳香化酶的良好竞争性抑制剂(Ki≤100 nM),通过气相色谱-质谱分析获得的芳香化率分别为 110 和 205pmol/min/mg。相反,6β-甲基异构体 12 和 14 是非竞争性抑制剂,Ki 值超过 500 nM,它们的芳香化率分别为 16 和 20 pmol/min/mg。这些结果表明,19-氧代 6α- 甲基和 6β- 甲基抑制剂与活性位点的结合存在明显差异,其中 6α- 类固醇而非 6β- 异构体的结合方式适合作为芳香化酶的底物。