THE ROLE OF CYTOCHROME P-450 ENZYMES IN CARCINOGENESIS

微粒体细胞色素P-450是一个酶家族，其中一些 代谢外来化合物和化学致癌物。其中一些 酶可以被致癌化合物诱导。例如, 3-甲基胆蒽可诱导小鼠细胞色素P1-450和P3-450。 这些诱导酶代谢苯并(A)芘、芳香胺和其他 致癌物质。一些活性代谢物与DNA形成结合，因此 被认为会引发突变和致癌。我们建议 细胞色素P1-450和P3-450酶在同源和 异源细胞，并确定这些酶对 突变和细胞转化。 为此，我们构建了具有感染性的重组牛痘疫苗。 含有P1-450和P3-450全长cDNA的病毒。人与人 重组病毒感染的小鼠细胞呈高水平表达 免疫印迹法检测真核表达蛋白的表达。这个 表达的蛋白质具有酶活性，并且表现出可区分的特征 底物特性。我们还构建了重组逆转录病毒 含有细胞色素P1-450和P3-450。感染了这些病毒的细胞 重组子表达细胞色素P3-450。初步实验表明 这种蛋白质具有酶活性。该系统现在可以方便地 突变和转化分析。

Microsomal cytochrome P-450s are a family of enzymes, some of which metabolize foreign compounds and chemical carcinogens. Some of these enzymes are inducible by carcinogenic compounds. For example, 3-methylcholanthrene induces cytochromes P1-450 and P3-450 in the mouse. These induced enzymes metabolize benzo(a)pyrene, aryl amines and other carcinogens. Some of the active metabolites formed bind to DNA and thus are presumed to initiate mutagenesis and carcinogenesis. We propose to express the cytochrome P1-450 and P3-450 enzymes in homologous and heterologous cells and determine the contribution of these enzymes to mutation and cell transformation. For this purpose, we have constructed infectious recombinant vaccinia viruses containing the full length cDNAs of P1-450 and P3-450. Human and mouse cells infected with the recombinant viruses showed high level expression of the authentic proteins as detected by immunoblotting. The expressed proteins are enzymatically active and exhibit distinguishable substrate specificities. We have also constructed recombinant retroviruses containing the cytochromes P1-450 and P3-450. Cells infected with these recombinants express cytochrome P3-450. Preliminary experiments indicate that the protein is enzymatically active. This system is now amiable to mutation and transformation analysis.