Rosenblum J L, Irwin C L, Alpers D H
Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.
Am J Physiol. 1988 May;254(5 Pt 1):G775-80. doi: 10.1152/ajpgi.1988.254.5.G775.
Salivary-type amylase may significantly contribute to duodenal starch hydrolysis in exocrine pancreatic insufficiency, provided that gastric inactivation does not occur. We investigated the effect of starch and its hydrolytic products, therefore, on salivary amylase activity in vitro at low pH. When incubated at pH 3 in the presence of 1% starch, 56% of the initial activity of amylase purified from saliva remained after 60 min at 37 degrees C compared with only 6% without starch. Similar protection of amylolytic activity was observed using human milk, which also contains a salivary-type amylase. In addition, partially hydrolyzed starch protected salivary amylase activity at pH 3, and purified glucose oligomers ranging in length from two to seven glucose molecules protected amylase in a concentration-dependent manner. Lactose, sucrose, and glucose, however, were ineffective in sparing amylase. Starch protected amylase activity even in the presence of pepsin, and maltotriose conferred striking protection below pH 3. These studies indicate that salivary-type isoamylases are protected in a simulated gastric environment by substrates of amylase as well as its end products of hydrolysis.
在不存在胃失活的情况下，唾液型淀粉酶可能对胰腺外分泌功能不全时十二指肠淀粉水解有显著贡献。因此，我们研究了淀粉及其水解产物在体外低pH条件下对唾液淀粉酶活性的影响。在37℃下于pH 3且存在1%淀粉的条件下孵育时，从唾液中纯化的淀粉酶在60分钟后仍保留其初始活性的56%，而无淀粉时仅保留6%。使用同样含有唾液型淀粉酶的人乳也观察到了类似的对淀粉分解活性的保护作用。此外，部分水解的淀粉在pH 3时能保护唾液淀粉酶活性，长度为2至7个葡萄糖分子的纯化葡萄糖寡聚物以浓度依赖的方式保护淀粉酶。然而，乳糖、蔗糖和葡萄糖对保护淀粉酶无效。即使在存在胃蛋白酶的情况下，淀粉也能保护淀粉酶活性，麦芽三糖在pH 3以下提供显著的保护作用。这些研究表明，在模拟胃环境中，唾液型异淀粉酶受到淀粉酶底物及其水解终产物的保护。
