Wainfan E, Kilkenny M, Dizik M
Lindsley F. Kimball Research Institute, New York Blood Center, NY 10021.
Carcinogenesis. 1988 May;9(5):861-3. doi: 10.1093/carcin/9.5.861.
The short-term effects of a lipotrope-deficient (methyl-deficient) diet on tRNA and protein methyltransferase activities have been studied using pair-fed male Fischer rats. The activity of liver N2-guanine tRNA methyltransferase II (NMG2) of animals receiving the methyl-deficient diet (MDD) for 2 weeks was found to be elevated more than 2-fold. This is in agreement with the results of earlier experiments in which the animals were fed ad libitum. These data indicate that the effects of lipotrope-deficient diets on NMG2 activity observed in the earlier studies can be attributed to the nature of the diet, and not to differences in caloric intake. In the same pair-fed animals, very little effect of MDD on the activity of NMG2 of either brain or spleen was observed. In liver, the activity of one of the enzymes that catalyze protein methylation--protein methylase I (S-adenosyl-methionine: protein-arginine N-methyltransferase)--was significantly elevated in response to the lipotrope-deficient diet. In contrast, the activities of protein methylase II (S-adenosylmethionine: protein-carboxy-O-methyltransferase), from control and experimental animals did not differ significantly. Lipotrope-deficient diets are thus seen to induce, within a short period of time, selective changes in the activities of some, but not all, of the liver enzymes that catalyze the methylation of tRNA and protein.
利用成对喂养的雄性Fischer大鼠，研究了缺乏促脂物质（甲基缺乏）饮食对tRNA和蛋白质甲基转移酶活性的短期影响。发现接受甲基缺乏饮食（MDD）2周的动物肝脏N2-鸟嘌呤tRNA甲基转移酶II（NMG2）的活性升高了2倍多。这与早期让动物自由进食的实验结果一致。这些数据表明，早期研究中观察到的缺乏促脂物质饮食对NMG2活性的影响可归因于饮食的性质，而非热量摄入的差异。在相同的成对喂养动物中，未观察到MDD对大脑或脾脏中NMG2活性有显著影响。在肝脏中，一种催化蛋白质甲基化的酶——蛋白质甲基化酶I（S-腺苷甲硫氨酸：蛋白质-精氨酸N-甲基转移酶）的活性因缺乏促脂物质饮食而显著升高。相比之下，对照动物和实验动物的蛋白质甲基化酶II（S-腺苷甲硫氨酸：蛋白质-羧基-O-甲基转移酶）的活性没有显著差异。因此，缺乏促脂物质的饮食在短时间内会诱导一些（但不是全部）催化tRNA和蛋白质甲基化的肝脏酶活性发生选择性变化。
