Felipoff A L, Río M E
J Nutr Sci Vitaminol (Tokyo). 1982 Oct;28(5):477-82. doi: 10.3177/jnsv.28.477.
The effect of dietary composition on the kinetic constants of intestinal lactase was studied using rats depleted of protein by feeding protein-free diet from the weanling stage to 34 days of age and subsequently allowed to recover on diets containing 11.5 or 17% of protein calories (P%) and different levels of lactose (L%; 1, 15, 27 and 37%). After four days of refeeding, rats were decapitated and lactase activity was determined at different substrate concentrations by the method of Dahlqvist using homogenate of intestinal mucosa. Maximum velocity (Vmax) and Michaelis constant (Km) were calculated according to Eisenthal and Cornish-Bowden. At both levels of P%, Vmax tended to increase with the dietary lactose concentration. With diets containing 37% lactose, at P% 11 Vmax was about 60% of that at P% 17.0 Km tended to increase with L% in groups given the 17.0% protein calorie diets, but no difference was observed between groups fed at the lower level of protein. These results can be explained on the basis of interactions between dietary protein at different concentrations and inducer substrate which results in changes in isoenzyme patterns.
通过从断奶期到34日龄给大鼠喂食无蛋白饮食使其蛋白质缺乏，随后让它们在含有11.5%或17%蛋白质热量（P%）以及不同水平乳糖（L%；1%、15%、27%和37%）的饮食上恢复，研究了饮食组成对肠道乳糖酶动力学常数的影响。重新喂食四天后，将大鼠断头，采用达尔奎斯特法，使用肠黏膜匀浆在不同底物浓度下测定乳糖酶活性。根据艾森塔尔和康沃尔-鲍登法计算最大速度（Vmax）和米氏常数（Km）。在两种P%水平下，Vmax均倾向于随饮食中乳糖浓度的增加而升高。对于含有37%乳糖的饮食，在P%为11时，Vmax约为P%为17时的60%。在给予17.0%蛋白质热量饮食的组中，Km倾向于随L%的增加而升高，但在低蛋白水平喂养的组之间未观察到差异。这些结果可以基于不同浓度的饮食蛋白质与诱导底物之间的相互作用来解释，这种相互作用导致了同工酶模式的变化。
