Properties of an adrenal cytochrome P-450 (P-45011beta) for the hydroxylations of corticosteroids.
Properties of an adrenal cytochrome P-450 (P-45011beta) for the hydroxylations of corticosteroids.
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肾上腺细胞色素 P-450 (P-45011beta) 对皮质类固醇羟基化的特性。
DOI：
10.1016/0003-9861(78)90280-1
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发表时间：
1978
影响因子：
3.9
通讯作者：
Masayuki Katagiri
中科院分区：
文献类型：
--
作者：
H. Sato;N. Ashida;K. Suhara;Eiji Itagaki;S. Takemori;Masayuki Katagiri
从牛肾上腺皮质线粒体中获得一种高纯度的细胞色素P-450，命名为P-45011β。P-45011β在由NADPH通过NADPH重建的肾上腺供电子系统中表现出非常高的类固醇羟化酶活性：肾上腺铁氧还蛋白氧化还原酶（EC 1.6.7.1）和肾上腺铁氧还蛋白。当脱氧皮质酮为底物时，11β-和18-羟化酶活性的转换数（每摩尔P-450-血红素每分钟形成的羟基化产物的摩尔数）分别为110和18。两种反应的表观Km值均为6 μ m。两种活性之间的比率约为6：1，在各种实验条件下是恒定的，包括在存在竞争性羟基化抑制剂的条件下。除脱氧皮质酮外，其他类固醇如11-脱氧皮质醇、4-雄烯-3，17-二酮和睾酮也是可羟基化的底物。在以4-雄甾烯-3，17-二酮（一种C19-类固醇）为底物的情况下，可羟基化位点似乎是其各自的11β-和19-位。这两种活动之间的比例约为4：1。根据这些结果，可以得出结论，P-45011β是一种血红素蛋白，负责各种皮质类固醇的羟化酶反应。2-甲基-1，2-二-3-吡啶基-1-丙酮（metyrapone）抑制P-45011β催化的11β-和18-位脱氧皮质酮或11β-和19-位4-雄烯-3，17-二酮的类固醇羟化酶反应（Ki= 0.1-0.2 μM）。P-450 SCC催化的胆固醇碳链酶反应也受到抑制，尽管很弱（Ki= 160 μM）。此外，这两种肾上腺细胞色素似乎在对甲吡酮的光谱反应中彼此不同。
A highly purified preparation of cytochromeP-450, designated asP-45011β, has been obtained from bovine adrenal cortex mitochondria. TheP-45011βexhibits remarkably high steroid hydroxylase activity in the reconstituted adrenal electron-donating system from NADPH via NADPH:adrenal ferredoxin oxidoreductase (EC 1.6.7.1) and adrenal ferredoxin. The turnover numbers (moles of hydroxylated product formed per minute per mole ofP-450-heme) are 110 and 18 for respective 11β- and 18-hydroxylase activity when deoxycorticosterone is the substrate. The apparentKmvalue is 6 μmfor both reactions. The ratio, about 6:1 between the two activities, is constant under various experimental conditions including those in the presence of competitive inhibitors of hydroxylation. In addition to deoxycorticosterone, other steroids such as 11-deoxycortisol, 4-androstene-3,17-dione and testosterone are the hydroxylatable substrates. In cases in which 4-androstene-3,17-dione, a C19-steroid, is the substrate, the hydroxylatable sites appear to be its respective 11β- and 19-position. The ratio between the two activities is about 4:1. In view of these results, it is concluded that one hemoprotein species, theP-45011β, is responsible for the hydroxylase reactions of various Corticosteroids. 2-Methyl-1,2-di-3-pyridyl-1-propanone (metyrapone) inhibits theP-45011β-catalyzed steroid hydroxylase reactions of either deoxycorticosterone at 11β- and 18-position or 4-androstene-3,17-dione at 11β- and 19-position (Ki= 0.1-0.2 μM). TheP-450scc-catalyzed cholesterol desmolase reaction is also inhibited, although weakly (Ki= 160 μM). In addition, both adrenal cytochromes appeared to differ from each other in spectral response to metyrapone.