ROLE OF CYTOCHROMES P-450 GENES IN MUTAGENESIS AND CARCINOGENESIS

细胞色素P-450超基因家族编码的酶 代谢一系列的外来物质，包括药物和 致癌物质，以及类固醇和前列腺素等内生生物。 在动物中，这些酶的多种形式表现出广泛的和 重叠的底物特异性同时被表达， 无论是结构性的还是在给予诱导剂之后。至 定义一个给定的细胞色素P-450对 对于特定药物和致癌物的代谢，重要的是要 在缺乏内源性的细胞中单独表达这些酶 这些酶的背景。为了实现这一目标，我们已经开始 发展单个细胞色素P-450的表达系统 蛋白质是由它们的编码DNA序列合成的。成功 这一努力将使我们能够确定每个人的贡献 这些酶的诱变和细胞转化 化学致癌物。为此，我们构建了 传染性重组痘苗病毒和传染性重组痘苗病毒 含有全长编码基因的逆转录病毒 小鼠细胞色素P1-450和P3-450。感染人和小鼠的细胞 用重组病毒高水平表达的正品 具有酶活性并展示的大小蛋白质 每种酶的底物特异性诊断。 初步实验表明，细胞色素P3-450选择性地 激活杂环芳胺和细胞色素P1-450 优先活化芳香烃；并且这一性质 在限制底物时似乎是相互排斥的 浓度。此外，细胞色素P3-450活性食品 诱变剂与表达细胞的DNA形成特异的加合物 P3-450。检测到的DNA加合物与 在体内给药后在小鼠或大鼠肝脏中形成 食物诱变剂。

The cytochrome P-450 supergene family codes for enzymes which metabolize a wide array of both xenobiotics including drugs and carcinogens, and endobiotics such as steroids and prostaglandins. In animals, multiple forms of these enzymes exhibiting broad and overlapping substrate specificities are expressed simultaneously, either constitutively or after administration of inducers. To define the contribution of a given cytochrome P-450 to the metabolism of specific drugs and carcinogens, it is important to express these enzymes individually in cells which lack endogenous background for these enzymes. Toward this goal we have begun to develop expression systems in which an individual cytochrome P-450 protein is synthesized from their coding DNA sequences. Success in this effort will enable us to define the contribution of each of these enzymes to mutagenesis and to cell transformation by chemical carcinogens. For this purpose, we have constructed infectious recombinant vaccinia virus and infectious recombinant retrovirus containing the full length coding cDNA sequences for mouse cytochrome P1-450 and P3-450. Human and mouse cells infected with the recombinant viruses expressed high levels of the authentic size proteins that were enzymatically active and displayed substrate specificities diagnostic of the respective enzymes. Preliminary experiments indicate that cytochrome P3-450 selectively activates heterocyclic arylamines and cytochrome P1-450 preferentially activates aromatic hydrocarbons; and this property appears to be mutually exclusive at limiting substrate concentrations. Furthermore, the cytochrome P3-450-activated food mutagens formed specific adducts with the DNA of cells expressing the P3-450. The DNA adducts detected were identical to those formed in mouse or rat liver after the in vivo administration of the food mutagens.