Nicholson J A, McCarthy D M, Kim Y S
J Clin Invest. 1974 Oct;54(4):890-8. doi: 10.1172/JCI107828.
The effects of variation in dietary protein content on small intestinal brush border and cytosol peptide hydrolase activities have been investigated. One group of rats was fed a high protein diet (55% casein) and another group was fed a low protein diet (10% casein). After 1 wk, brush border peptide hydrolase activity (L-leucyl-beta-naphthylamide as substrate) and cytosol peptide hydrolase activity (L-prolyl-L-leucine as substrate) were determined in mucosae taken from the proximal, middle, and distal small intestine. As judged by several parameters, brush border peptide hydrolase activity was significantly greater in rats fed the high protein diet when data for corresponding segments were compared. In contrast, no significant difference was seen in cytosol peptide hydrolase activity. IN A SECOND STUDY, BRUSH BORDER AND CYTOSOL PEPTIDE HYDROLASE ACTIVITIES WERE DETERMINED IN THE PROXIMAL INTESTINE BY UTILIZING AN ADDITIONAL THREE PEPTIDE SUBSTRATES: L-leucyl-L-alanine, L-phenylalanylglycine, and glycyl-L-phenylalanine. Sucrase, maltase, and alkaline phosphatase activities were also determined. As before, brush border peptide hydrolase activities were significantly greater in rats fed the high protein diet. However, activities of the nonproteolytic brush border enzymes did not vary significantly with diet. In contrast to the results obtained with L-prolyl-L-leucine as substrate for the cytosol enzymes, cytosol activity against the three additional peptide substrates was greater in rats fed the high protein diet. It is suggested that the brush border peptide hydrolase response to variation in dietary protein content represents a functional adaptation analogous to the regulation of intestinal disaccharidases by dietary carbohydrates. The implication of the differential responses of the cytosol peptide hydrolases is uncertain, since little is known of the functional role of these nonorgan-specific enzymes.
研究了日粮蛋白质含量变化对小肠刷状缘和胞质溶胶肽水解酶活性的影响。一组大鼠饲喂高蛋白日粮（55%酪蛋白），另一组大鼠饲喂低蛋白日粮（10%酪蛋白）。1周后，测定取自近端、中部和远端小肠黏膜的刷状缘肽水解酶活性（以L-亮氨酰-β-萘酰胺为底物）和胞质溶胶肽水解酶活性（以L-脯氨酰-L-亮氨酸为底物）。通过几个参数判断，当比较相应节段的数据时，饲喂高蛋白日粮的大鼠刷状缘肽水解酶活性显著更高。相比之下，胞质溶胶肽水解酶活性未见显著差异。在第二项研究中，通过使用另外三种肽底物：L-亮氨酰-L-丙氨酸、L-苯丙氨酰甘氨酸和甘氨酰-L-苯丙氨酸，测定近端小肠的刷状缘和胞质溶胶肽水解酶活性。还测定了蔗糖酶、麦芽糖酶和碱性磷酸酶活性。和之前一样，饲喂高蛋白日粮的大鼠刷状缘肽水解酶活性显著更高。然而，非蛋白水解性刷状缘酶的活性并未随日粮而显著变化。与以L-脯氨酰-L-亮氨酸作为胞质溶胶酶底物所获得的结果相反，饲喂高蛋白日粮的大鼠针对另外三种肽底物的胞质溶胶活性更高。有人提出，刷状缘肽水解酶对日粮蛋白质含量变化的反应代表了一种功能适应性，类似于日粮碳水化合物对肠道二糖酶的调节。胞质溶胶肽水解酶的不同反应的意义尚不确定，因为对这些非器官特异性酶的功能作用了解甚少。
