Chiang J Y, Malmer M, Hutterer F
Biochim Biophys Acta. 1983 Feb 7;750(2):291-9. doi: 10.1016/0005-2760(83)90031-0.
A form of cytochrome P-450 which comigrates with cytochrome P-450LM4 (molecular weight, 55 000) on SDS-polyacrylamide gel was purified from liver microsomes of cholestyramine-treated rabbits. This form of cytochrome P-450 catalyzed the 7 alpha-hydroxylation of cholesterol with an activity of 37.5 pmol/min per nmol cytochrome P-450 in the reconstituted enzyme system containing cytochrome P-450 and NADPH-cytochrome P-450 reductase. The substrate specificity of this form of cytochrome P-450 was compared with cytochrome P-450LM4 isolated from phenobarbital- and beta-naphthoflavone-treated rabbit liver microsomes. The latter two isoenzymes do not catalyze 7 alpha-hydroxylation of cholesterol, but are more active in O-deethylation of 7-ethoxycoumarin and p-nitrophenetole. Ouchterlony double diffusion revealed cross-reactivity between anti-P-450LM4 (phenobarbital) IgG and cytochrome P-450 isolated from cholestyramine- or beta-naphthoflavone-treated rabbit liver microsomes. A two-dimensional iodinated tryptic peptide fingerprint indicated only minor structural differences among these three cytochrome P-450LM4 preparations.
从消胆胺处理的兔肝脏微粒体中纯化出一种细胞色素P - 450，它在SDS - 聚丙烯酰胺凝胶上与细胞色素P - 450LM4（分子量55000）一同迁移。在含有细胞色素P - 450和NADPH - 细胞色素P - 450还原酶的重组酶系统中，这种细胞色素P - 450催化胆固醇的7α - 羟化反应，活性为每nmol细胞色素P - 450 37.5 pmol/分钟。将这种细胞色素P - 450的底物特异性与从苯巴比妥和β - 萘黄酮处理的兔肝脏微粒体中分离出的细胞色素P - 450LM4进行了比较。后两种同工酶不催化胆固醇的7α - 羟化反应，但在7 - 乙氧基香豆素和对硝基苯乙醚的O - 脱乙基反应中活性更高。免疫双扩散试验显示，抗P - 450LM4（苯巴比妥）IgG与从消胆胺或β - 萘黄酮处理的兔肝脏微粒体中分离出的细胞色素P - 450之间存在交叉反应。二维碘化胰蛋白酶肽指纹图谱表明，这三种细胞色素P - 450LM4制剂之间仅存在微小的结构差异。
