Stereochemical specificity at carbon‐20 and ‐22 of hydroxylated cholesterols for side‐chain cleavage by adrenocortical cytochrome P‐450scc
Stereochemical specificity at carbon‐20 and ‐22 of hydroxylated cholesterols for side‐chain cleavage by adrenocortical cytochrome P‐450scc
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肾上腺皮质细胞色素 P-450scc 进行侧链裂解时羟基化胆固醇在碳 20 和 22 处的立体化学特异性
DOI：
10.1016/0014-5793(76)80999-4
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发表时间：
1976
期刊：
影响因子：
3.5
通讯作者：
N. Ikekawa
中科院分区：
文献类型：
--
作者：
M. Morisaki;Susumu Sato;N. Ikekawa
胆固醇酶促转化为孕烯醇酮是各种类固醇激素生物合成的第一步。许多工作者对这一重要生物反应的机制进行了研究，大多使用粗酶制剂，如肾上腺皮质线粒体丙酮干粉。最近，从牛肾上腺皮质线粒体中纯化出具有将胆固醇转化为孕烯醇酮的酶活性的细胞色素P-450 [1, 2]。通过使用这种纯化的细胞色素 P-4.50（胆固醇 20, 22-裂解酶），我们之前已经证明 [3]，与 Kraaipoel 的假设相反 [4, 5]，20, 22-环氧胆固醇’和 20 (22)-脱氢胆固醇都不是胆固醇和前烯醇酮之间的中间体。 Burstein 等人独立得出了类似的结论[6]。关于羟基胆固醇被认为是裂解反应中间体的作用，最近引起了一些争议[7-9]。我们现在已经合成了20-羟基胆固醇、22-羟基胆固醇和20, 22-~羟基胆固醇1的所有C-20和/或C-22立体异构体（图1），并将它们与细胞色素P-450一起孵育，在存在NADPH 生成和电子传输系统。我们的目的是了解立体化学特性
The enzymatic conversion of cholesterol to pregnenolone is the initial step of biosynthesis of various steroid hormones. The mechanism of this important biological reaction has been studied by many workers mostly with crude enzyme preparations such as adrenocortical mitochondrial acetone-dried powders. Recently, a cytochrome P-450 which has an enzyme activity of converting cholesterol to pregnenolone has been purified from bovine adrenocortical mitochondria [1, 2]. By the use of this purified cytochrome P-4.50,(cholesterol 20, 22-lyase), we have previously shown [3] that, in contradiction to Kraaipoel’s hypothesis [4, 5], neither 20, 22-epoxycholesterol’nor 20 (22)-dehydrocholesterol could be the intermediate between cholesterol and pre~ enolone. A similar conclusion was independently obtained by Burstein et al.[6]. On the role of hydroxycholesterols which have been postulated as the intermediates of the cleavage reaction, some controversy was recently raised [7-9].We have now synthesized all the C-20 and/or C-22 stereoisomers of 20-hydroxycholesterol, 22-hydroxycholesterol and 20, 22-~ hydroxychoIestero1(fig. l), and incubated them with cytochrome P-450, in the presence of NADPH generating and electron transport systems. Our aim was to know stereochemicai specifi-