HUMAN-LIVER MICROSOMAL STEROID-METABOLISM - IDENTIFICATION OF THE MAJOR MICROSOMAL STEROID-HORMONE 6-BETA-HYDROXYLASE CYTOCHROME-P-450 ENZYME
HUMAN-LIVER MICROSOMAL STEROID-METABOLISM - IDENTIFICATION OF THE MAJOR MICROSOMAL STEROID-HORMONE 6-BETA-HYDROXYLASE CYTOCHROME-P-450 ENZYME
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DOI：
10.1016/0003-9861(88)90655-8
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发表时间：
1988-06-01
影响因子：
3.9
通讯作者：
LAPENSON, DP
中科院分区：
文献类型：
--
作者：
WAXMAN, DJ;ATTISANO, C;LAPENSON, DP
在分离的人肝微体部分研究了细胞色素P-450依赖的类固醇激素代谢。6.测试版。羟化是NADPH依赖的氧化代谢的主要途径(gtoreq.总羟化代谢物的75%)与三种类固醇底物--睾酮、雄烯二酮和孕酮--的每一种。加上睾丸素，2.beta。和15.测试版。羟基化也发生了，在.apprx处进行。微粒体率分别为10%和3-4%。分别在每个被检查的肝脏样本中进行羟化。3种类固醇6β-羟基酶活性的比率彼此高度相关(25个单独的微粒体制剂的r=0.95-0.97)，这表明单一的人肝P-450酶是所有三种类固醇底物的主要微粒体6β-羟基酶催化剂。类固醇6-羟基酶活性与人P-450NF的比含量(r=0.69-0.83)及其相关的硝苯地平氧化酶活性(r=0.80)有很好的相关性，但与Debrisquine 4-羟基酶、非那西丁O-脱乙基酶或S-美苯妥因4-羟基酶的活性或它们各自相关的P-450形式的比含量在这些肝微体中的比含量无关(r<；0.2)。这些纠正的观察结果得到了对人肝微粒体6β的选择性抑制的支持。通过抗体进行羟基化，可以提高人P-450NF或大鼠同系物P-450PB-2a的活性。抗P-450NF还能抑制人微粒体睾酮2β的表达。和15.测试版。与6β-羟基化反应平行的羟化反应。该抗体对大鼠P-450 2a依赖的类固醇激素6β也有抑制作用。未诱导的成年雄性大鼠肝微粒体中的羟化，但不包括类固醇2α、16α或7α。其他形式的大鼠P-450催化的羟基化反应。最后是类固醇6.beta。大环内酯类抗生素三乙酰齐兰霉素的NADPH依赖络合反应选择性地抑制了人或大鼠肝微粒体催化的羟化反应，这是P-450NF基因亚家族(P-450 IIIA亚家族)成员特有的反应。这些观察结果表明，P-450NF或一种密切相关的酶是类固醇激素6β的主要催化剂。人肝微粒体中的羟基化，并进一步表明类固醇6β。羟化作用可能为这种肝脏P-450形式的单加氧酶活性提供有用的、非侵入性的监测。
Cytochrome P-450-dependent steroid hormone metabolism was studied in isolated human liver microsomal fractions. 6.beta. hydroxylation was shown to be the major route of NADPH-dependent oxidative metabolism (.gtoreq. 75% of total hydroxylated metabolites) with each of three steroid substrates, testosterone, androstenedione, and progesterone. With testosterone, 2.beta. and 15.beta. hydroxylation also occurred, proceeding at .apprx. 10% and 3-4% the rate of microsomal 6.beta. hydroxylation, respectively, in each of the liver samples examined. Rates for the three steroid 6.beta.-hydroxylase activities were highly correlated with each other (r = 0.95-0.97 for 25 individual microsomal preparations), suggesting that a single human liver P-450 enzyme is the principal microsomal 6.beta.-hydroxylase catalyst with all three steroid substrates. Steroid 6.beta.-hydroxylase rates correlated well with the specific content of human P-450NF (r = 0.69-0.83) and with its associated nifedipine oxidase activity (r = 0.80), but not with the rates for debrisoquine 4-hydroxylase, phenacetin O-deetylase, or S-mephenytoin 4-hydroxylase activities or the specific contents of their respective associated P-450 forms in these same liver microsomes (r < 0.2). These corrective observations were supported by the selective inhibition of human liver microsomal 6.beta. hydroxylation by antibody raised either human P-450NF or a rat homolog, P-450 PB-2a. Anti-P-450NF also inhibited human microsomal testesterone 2.beta. and 15.beta. hydroxylation in parallel to the 6.beta.-hydroxylation reaction. This antibody also inhibited rat P-450 2a-dependent steroid hormone 6.beta. hydroxylation in uninduced adult male rat liver microsomes but not the steroid 2.alpha., 16.alpha., or 7.alpha. hydroxylation reactions catalyzed by other rat P-450 forms. Finally, steroid 6.beta. hydroxylation catalyzed by either human or rat liver microsomes was selectively inhibited by NADPH-dependent complexation of the macrolide antibiotic triacetyloleandomycin, a reaction that is characteristic of members of the P-450NF gene subfamily (P-450 IIIA subfamily). These observations establish that P-450NF or a closely related enzyme is the major catalyst of steroid hormone 6.beta. hydroxylation in human liver microsomes, and furthermore suggest that steroid 6.beta. hydroxylation may provide a useful, noninvasive monitor for the monooxygenase activity of this hepatic P-450 form.