Tsuda M, Frank N, Sato S, Sugimura T
Biochemistry Division, National Cancer Center Research Institute, Tokyo, Japan.
Cancer Res. 1988 Jul 15;48(14):4049-52.
When five volunteers were given food containing cod and vegetables (a traditional Japanese food, called tara-chiri), their urinary excretion of N-nitrosothioproline increased from 7.9 +/- 4.2 (SD) micrograms/day to 110 +/- 64.5 micrograms/day. This increase was accounted for by in vivo nitrosation of of thioproline by nitrite formed from nitrate in the vegetables. This finding was confirmed by results on a volunteer who ate boiled cod and Japanese radish (daikon) (a simple version of the food containing cod and vegetables). Boiled cod was found to contain 300-500 micrograms/100 g of thioproline, and the level nearly doubled when the cod was boiled with Japanese radish. This increase occurred during the cooking of cod with Japanese radish by the reaction of formaldehyde in the cod with cysteine in the Japanese radish. The nitrosation of thioproline was estimated to be 1000-fold that of proline in the human body. Thus thioproline is a very sensitive probe of in vivo nitrosation. Thioproline formation either in vivo or in vitro may have the following two roles in reducing tumorigenesis in humans: (a) detoxication of formaldehyde, which is genotoxic; and (b) blocking the formation of carcinogenic N-nitroso compounds by trapping nitrite and then being excreted in the urine.
当五名志愿者食用含有鳕鱼和蔬菜的食物（一种传统日本食物，称为鳕鱼杂烩）时，他们尿中N-亚硝基硫代脯氨酸的排泄量从7.9±4.2（标准差）微克/天增加到110±64.5微克/天。这种增加是由蔬菜中的硝酸盐形成的亚硝酸盐在体内对硫代脯氨酸进行亚硝化作用所致。一名食用煮鳕鱼和日本萝卜（大根）（鳕鱼和蔬菜食物的简单版本）的志愿者的结果证实了这一发现。发现煮鳕鱼每100克含有300 - 500微克硫代脯氨酸，当鳕鱼与日本萝卜一起煮时，该水平几乎翻倍。这种增加是在鳕鱼与日本萝卜烹饪过程中，鳕鱼中的甲醛与日本萝卜中的半胱氨酸反应产生的。据估计，硫代脯氨酸的亚硝化作用在人体中是脯氨酸的1000倍。因此，硫代脯氨酸是体内亚硝化作用的一个非常敏感的指标。硫代脯氨酸在体内或体外形成可能在降低人类肿瘤发生方面具有以下两个作用：（a）对具有基因毒性的甲醛进行解毒；（b）通过捕获亚硝酸盐然后经尿液排出，阻止致癌性N-亚硝基化合物的形成。
