DeNigris S J, Hamosh M, Kasbekar D K, Fink C S, Lee T C, Hamosh P
Biochim Biophys Acta. 1985 Aug 22;836(1):67-72. doi: 10.1016/0005-2760(85)90221-8.
The presence of a triacylglycerol lipase in human gastric juice was described in previous studies. Its source and role in intragastric lipolysis was, however, uncertain. Our study presents definitive evidence for gastric origin of a lipase and its release by secretagogues. Both carbachol and cholecystokinin-8 stimulate release of this enzyme for dispersed human gastric glands. While the two secretagogues had similar efficacies, with nearly a 3-fold stimulation over basal rates, cholecystokinin-8 was about four orders of magnitude more potent in releasing lipolytic activity than carbachol (maximum stimulation at concentrations of 1 X 10(-9) and 1 X 10(-5) M, respectively). Lipolytic activity measured against triolein (18:1), tricaprylin (8:0) and tributyrin (4:0) emulsions was 1.18 +/- 0.12, 4.48 +/- 0.64, and 12.17 +/- 0.88 units (1 unit = 1 mumol free fatty acid released/min per mg protein), respectively. Characterization of the pH optimum for each substrate showed maximum lipolysis at 4.5 for tributyrin, and at 5.5 for tricaprylin and triolein. These results indicate that a lipase which hydrolyzes long-, medium- and short-chain triacylglycerols is secreted by human gastric mucosa. At pH 6.0, the pH of the duodenum, there is appreciable lipolytic activity in the presence of bile salts. This suggests that gastric lipase, in addition to initiating lipolysis in the stomach, might also aid in the digestion of lipids in the duodenum. It remains to be determined whether gastric lipase is distinct from lingual lipase, or is the same enzyme secreted by the lingual serous glands and the gastric mucosa.
先前的研究报道了人胃液中存在三酰甘油脂肪酶。然而，其来源及在胃内脂肪分解中的作用尚不确定。我们的研究为一种脂肪酶的胃源性及其由促分泌素释放提供了确凿证据。卡巴胆碱和八肽胆囊收缩素均可刺激分散的人胃腺释放这种酶。虽然这两种促分泌素具有相似的效力，比基础速率刺激近3倍，但八肽胆囊收缩素在释放脂肪分解活性方面比卡巴胆碱强约四个数量级（分别在1×10⁻⁹和1×10⁻⁵M浓度下达到最大刺激）。以三油精（18:1）、三辛酸甘油酯（8:0）和三丁酸甘油酯（4:0）乳剂测定的脂肪分解活性分别为1.18±0.12、4.48±0.64和12.17±0.88单位（1单位=每分钟每毫克蛋白质释放1μmol游离脂肪酸）。对每种底物的最适pH进行表征显示，三丁酸甘油酯在pH 4.5时脂肪分解最大，三辛酸甘油酯和三油精在pH 5.5时脂肪分解最大。这些结果表明，人胃黏膜分泌一种可水解长链、中链和短链三酰甘油的脂肪酶。在十二指肠pH 6.0时，在胆汁盐存在下有明显的脂肪分解活性。这表明胃脂肪酶除了在胃中启动脂肪分解外，还可能有助于十二指肠中脂质的消化。胃脂肪酶是否与舌脂肪酶不同，或者是否是舌浆液腺和胃黏膜分泌的同一种酶，仍有待确定。
