Response of rat pancreatic proteases to dietary proteins, their hydrolysates and soybean trypsin inhibitor.
Response of rat pancreatic proteases to dietary proteins, their hydrolysates and soybean trypsin inhibitor.
复制标题
大鼠胰腺蛋白酶对膳食蛋白质、其水解产物和大豆胰蛋白酶抑制剂的反应。
DOI：
10.1093/jn/114.2.270
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
C. Mettraux
中科院分区：
文献类型：
--
作者：
R. Temler;C. Dormond;E. Simon;B. Morel;C. Mettraux
本研究旨在确定胰腺胰蛋白酶和凝乳胰蛋白酶活性对膳食蛋白质水平的适应性是否可归因于饮食中作为这些酶底物的特定肽键的存在。此外，由于已知该化合物可刺激胰腺蛋白酶的合成，因此对饲喂大豆胰蛋白酶抑制剂（SBTI）的效果进行了测试。3周后，分别饲喂含有10%、20%或30%蛋白质的乳蛋白饲料（对照组）；乳蛋白经胰蛋白酶、凝乳胰蛋白酶或胰酶预消化；氨基酸混合物：氨基酸的混合物；或添加SBTI的乳清蛋白。实验结束时，测定大鼠胰腺匀浆中胰蛋白酶、胰凝乳蛋白酶和淀粉酶的活性。饲喂预消化乳清蛋白和乳清蛋白时，各蛋白质水平下胰蛋白酶和凝乳胰蛋白酶的活性完全相同，但添加20%和30%氨基酸时，两种蛋白酶的活性均有所降低。SBTI使这两种蛋白酶在所有三种蛋白水平上的活性增加了一倍。淀粉酶活性在20%蛋白质水平时达到最大值。由此可见，胰腺蛋白酶对饲粮蛋白质水平的适应是由饲粮蛋白质消化产物小肽诱导的。因此，胰腺胰蛋白酶或凝乳胰蛋白酶的诱导不需要肠道中这些酶的底物存在。与蛋白质或多肽相比，饲料中SBTI产生的胰腺蛋白酶显著增加。这表明，无论是富含蛋白质的饮食还是SBTI引起的胰腺蛋白酶的增加都是由两种不同的机制介导的。
The present study was designed to determine whether the adaptation of pancreatic trypsin and chymotrypsin activities to dietary protein level can be attributed to the presence in the diet of the specific peptide bonds that are substrates for these enzymes. In addition, the effect of feeding soybean trypsin inhibitor (SBTI) was tested since this compound is known to stimulate synthesis of pancreatic proteases. For 3 weeks, rats were fed a diet containing 10, 20 or 30% protein as lactalbumin (control); lactalbumin predigested by trypsin, chymotrypsin or pancreatin; a mixture of amino acids; or lactalbumin supplemented with SBTI. At the end of the experiment, the activities of trypsin, chymotrypsin and amylase were determined in the rats' pancreatic homogenates. Trypsin and chymotrypsin activities at each protein level were exactly the same whether predigested lactalbumin or lactalbumin was fed. The 20 and 30% amino acid mixtures, however, produced a decrease in activities of both proteases. SBTI doubled the activities of both proteases at all three levels of protein. Amylase activity was maximal at 20% level of protein. It is concluded that adaptation of pancreatic proteases to dietary protein level is induced by small peptides that are digestion products of dietary protein. Induction of pancreatic trypsin or chymotrypsin therefore does not require the presence of substrate for these enzymes in the intestine. Dietary SBTI produced a considerable increase in pancreatic proteases compared to that produced by proteins or peptides. It is suggested that the increases in pancreatic proteases caused either by protein-rich diets or SBTI are mediated by two distinct mechanisms.