Kim S, Lotlikar P D, Chin W, Magee P N
Fels Research Institute, Temple University School of Medicine, Philadelphia, Pa 19140.
Cancer Lett. 1977 Mar;2(4-5):279-84. doi: 10.1016/s0304-3835(77)80033-5.
Protein modification with dimethylnitrosamine was studied in vitro in the presence of hamster liver microsomal fraction. Incorporation of radioactive methyl groups from dimethylnitrosamine into the exogenously added protein was dependent on the microsomal mixed function oxidase system. The methylation yielded chemically labile and stable products. The former was completely hydrolyzed by the mild alkaline treatment, pH 7.4, 100 degrees C, for 5 min and the hydrolytic product was identified as methanol indicating that the activated methyl groups from dimethylnitrosamine were incorporated into a protein as a carboxyl-methyl ester. Thus, it is suggested that methanol, recovered as one of the products during the biodegradation of dimethylnitrosamine [8], is derived, at least in part, from protein carboxyl-methyl ester which is unstable under physiological conditions.
在仓鼠肝微粒体组分存在的情况下，对二甲基亚硝胺进行蛋白质修饰的体外研究。二甲基亚硝胺中放射性甲基掺入到外源添加的蛋白质中取决于微粒体混合功能氧化酶系统。甲基化产生了化学不稳定和稳定的产物。前者在pH 7.4、100℃温和碱性处理5分钟后完全水解，水解产物被鉴定为甲醇，这表明二甲基亚硝胺的活化甲基以羧甲基酯的形式掺入到蛋白质中。因此，有人提出，在二甲基亚硝胺生物降解过程中作为产物之一回收的甲醇，至少部分来源于在生理条件下不稳定的蛋白质羧甲基酯。
