Thiruvengadam R, DiMagno E P
Division of Gastroenterology, Mayo Clinic, Rochester, Minnesota.
Am J Physiol. 1988 Oct;255(4 Pt 1):G476-81. doi: 10.1152/ajpgi.1988.255.4.G476.
To determine if human lipase is inactivated by trypsin and chymotrypsin, we intubated 22 human subjects with an oroduodenal tube and stimulated pancreatic secretion with cholecystokinin octapeptide. The duodenal aspirate from each subject was divided into a control and a test sample and incubated in a 37 degrees C water bath for 2 h. An inhibitor of trypsin or chymotrypsin or more of one of these enzymes was added to the test sample. We found that the loss of lipase activity was partly prevented by inhibiting trypsin with aprotinin (910 KU/ml; P = 0.03) and was accelerated by adding bovine trypsin (2.5 mg/ml; P = 0.01). Inhibiting chymotrypsin with turkey egg white (2.5 mg/ml) totally abolished the loss of lipase activity (P = 0.01), and addition of bovine chymotrypsin (5 mg/ml) accelerated the loss of lipase activity more than adding trypsin (P = 0.01). After inhibiting chymotrypsin (to maintain lipase activity), increasing trypsin activity by adding a single or repeated doses of trypsin did not decrease lipase activity. Conversely, the addition of a single dose of chymotrypsin after inhibiting trypsin activity markedly decreased lipase activity (P less than 0.004). In conclusion, chymotrypsin is a more potent inactivator of human lipase than trypsin; chymotrypsin inactivates lipase in the absence of trypsin, but trypsin inactivation of lipase requires chymotrypsin.
为了确定人脂肪酶是否会被胰蛋白酶和糜蛋白酶灭活，我们用一根经口十二指肠管给22名人类受试者插管，并使用八肽胆囊收缩素刺激胰腺分泌。将每位受试者的十二指肠抽吸物分为对照样本和测试样本，并在37℃水浴中孵育2小时。向测试样本中加入胰蛋白酶或糜蛋白酶的抑制剂或更多的其中一种酶。我们发现，用抑肽酶（910KU/ml；P = 0.03）抑制胰蛋白酶可部分阻止脂肪酶活性的丧失，而加入牛胰蛋白酶（2.5mg/ml；P = 0.01）则会加速其丧失。用火鸡蛋清（2.5mg/ml）抑制糜蛋白酶可完全消除脂肪酶活性的丧失（P = 0.01），加入牛糜蛋白酶（5mg/ml）比加入胰蛋白酶更能加速脂肪酶活性的丧失（P = 0.01）。在抑制糜蛋白酶（以维持脂肪酶活性）后，通过单次或重复剂量加入胰蛋白酶来增加胰蛋白酶活性并不会降低脂肪酶活性。相反，在抑制胰蛋白酶活性后加入单次剂量的糜蛋白酶会显著降低脂肪酶活性（P＜0.004）。总之，糜蛋白酶是人脂肪酶比胰蛋白酶更有效的灭活剂；糜蛋白酶在没有胰蛋白酶的情况下可使脂肪酶失活，但胰蛋白酶使脂肪酶失活需要糜蛋白酶。
