Izotov M V, Shcherbakov V M, Devichensky V M, Spiridonova S M, Lugovaja L V, Benediktova S A
Institute of Applied Molecular Biology, Moscow, USSR.
Biotechnol Appl Biochem. 1988 Dec;10(6):545-50.
A method for measuring the content of two groups of microsomal cytochrome P-450 isozymes--cytochromes P-450W and P-450L--with the active sites directed into the water phase and membrane lipids, respectively, has been developed. The method is based on the ability of the xanthine oxidase-menadione complex to reduce microsomal cytochromes b5 and P-450 under anaerobic conditions by transferring electrons to hemoproteins with the active sites directed into the water phase. Cytochrome b5 is completely reduced (to the dithionite level) and cytochrome P-450 is reduced partially (only a group of cytochromes P-450W). The amount of cytochromes P-450L is estimated using the difference between the total content of cytochrome P-450 reduced by sodium dithionite and the content of cytochromes P-450W. The possibility of controlling the ratio of these two isozyme groups in cytochrome P-450 in vivo in membranes of the endoplasmic reticulum by pretreatment of animals with a variety of chemicals has been demonstrated. The ratio of cytochromes P-450W and P-450L has been shown to decrease two-fold 18 days after three injections of phenobarbital into mice. Carbon tetrachloride and cyclophosphamide also decrease this ratio in vivo.
已开发出一种测量两组微粒体细胞色素P-450同工酶——细胞色素P-450W和P-450L——含量的方法，其活性位点分别朝向水相和膜脂。该方法基于黄嘌呤氧化酶-甲萘醌复合物在厌氧条件下通过将电子转移至活性位点朝向水相的血红素蛋白来还原微粒体细胞色素b5和细胞色素P-450的能力。细胞色素b5被完全还原（至连二亚硫酸钠水平），而细胞色素P-450被部分还原（仅一组细胞色素P-450W）。细胞色素P-450L的含量通过连二亚硫酸钠还原的细胞色素P-450总含量与细胞色素P-450W含量之间的差值来估算。已证明通过用多种化学物质对动物进行预处理来控制内质网膜中细胞色素P-450体内这两种同工酶组比例的可能性。已表明，给小鼠注射三次苯巴比妥后18天，细胞色素P-450W和P-450L的比例降低了两倍。四氯化碳和环磷酰胺在体内也会降低这一比例。
