MODULATION OF THE ACTIVITY OF HUMAN 17-ALPHA-HYDROXYLASE-17,20-LYASE (CYP17) BY CYTOCHROME B(5) - ENDOCRINOLOGIC AND MECHANISTIC IMPLICATIONS
MODULATION OF THE ACTIVITY OF HUMAN 17-ALPHA-HYDROXYLASE-17,20-LYASE (CYP17) BY CYTOCHROME B(5) - ENDOCRINOLOGIC AND MECHANISTIC IMPLICATIONS
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DOI：
10.1042/bj3080901
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发表时间：
1995-06-15
影响因子：
4.1
通讯作者：
AKHTAR, M
中科院分区：
文献类型：
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作者：
LEEROBICHAUD, P;WRIGHT, JN;AKHTAR, M
使用 NADPH-细胞色素 P-450 还原酶作为电子供体，均质猪 17 α-羟化酶-17,20-裂解酶 (CYP17) 显示可催化 Delta(5) 以及 Delta(4)、类固醇（分别为孕烯醇酮和黄体酮）主要转化为相应的 17 α-羟基化产物。然后后者被酶的裂解酶（去氨酶）活性裂解成雄激素。细胞色素b(5) 刺激这两种活性，但其最显着的作用是对Delta(16)-类固醇的形成，这强制需要细胞色素b(5) 的存在。这些关于猪酶的结果证实了最初的发现 [Nakajin, Takahashi, Shinoda 和 Ha11 (1985) Biochem.生物物理学。资源。交流。 132、708-713]。人类 CYPI7 在大肠杆菌中表达 [Imai, Globerman, Gertner, Kakawa and Waterman (1993) J. Biol.化学。 268, 19681-19689] 也被纯化至均质，并且被发现可以催化孕烯醇酮和黄体酮的羟基化，而不需要细胞色素 b(5)。与猪 CYP17 一样，人 CYP17 也催化细胞色素 b(5) 依赖性的孕烯醇酮直接裂解为 Delta(5,16)-类固醇，但与它不同的是，人酶根本不裂解孕酮。然而，17 α-羟基孕烯醇酮仅在细胞色素 b(5) 存在的情况下才被裂解成相应的雄激素。 17 α-羟基孕酮是人类 CYP17 的不良底物；尽管在细胞色素 b(5) 存在的情况下它会转化为雄烯二酮，但其 K-m 和 V-max 高出 5 倍。比孕酮羟基化低2.6倍。讨论了这些结果的内分泌学和机制意义。
Using NADPH-cytochrome P-450 reductase as electron donor the homogeneous pig 17 alpha-hydroxylase-17,20-lyase (CYP17) was shown to catalyse the conversion of Delta(5), as well as Delta(4), steroids (pregnenolone and progesterone respectively) predominantly into the corresponding 17 alpha-hydroxylated products. The latter were then cleaved by the lyase (desmolase) activity of the enzyme into androgens. Cytochrome b(5) stimulated both these activities, but its most noticeable effect was on the formation of Delta(16)-steroids, which compulsorily required the presence of cytochrome b(5). These results on the pig enzyme confirm the original findings [Nakajin, Takahashi, Shinoda and Ha11 (1985) Biochem. Biophys. Res. Commun. 132, 708-713]. The human CYPI7 expressed in Escherichia coli [Imai, Globerman, Gertner, Kagawa and Waterman (1993) J. Biol. Chem. 268, 19681-19689] was also purified to homogeneity and was found to catalyse the hydroxylation of pregnenolone and progesterone without requiring cytochrome b(5). Like the pig CYP17, the human CYP17 also catalysed the cytochrome b(5)-dependent direct cleavage of pregnenolone into the Delta(5,16)-steroid, but unlike it the human enzyme did not cleave progesterone at all. 17 alpha-Hydroxypregnenolone was, however, cleaved into the corresponding androgen but only in the presence of cytochrome b(5). 17 alpha-Hydroxyprogesterone was a poor substrate for the human CYP17; although it was converted into androstenedione in the presence of cytochrome b(5) its K-m was 5 times higher and V-max. 2.6 times lower than those for the hydroxylation of progesterone. The endocrinological and mechanistic implications of these results are discussed.