In vivo and in vitro studies on the stereoselective hydrolysis of tri- and diglycerides by gastric and pancreatic lipases
In vivo and in vitro studies on the stereoselective hydrolysis of tri- and diglycerides by gastric and pancreatic lipases
复制标题
DOI：
10.1016/s0968-0896(96)00251-9
复制
发表时间：
1997-02-01
影响因子：
3.5
通讯作者：
Verger, R
中科院分区：
文献类型：
--
作者：
Carriere, F;Rogalska, E;Verger, R
在体外，模拟生理条件下，和在体内，在液体试验餐的消化过程中，研究了狗胃脂肪酶和狗胰腺脂肪酶的立体选择性。在体外观察到，尽管这两种脂肪酶都有甘油三酯中sn-3位置的立体参照，但在胃脂肪酶中它大约高出三倍。另一方面，当外消旋双油油作底物时，两种脂肪酶对sn-1位显示出类似的对映体选择性。在胰腺脂肪酶的情况下，由于进一步的立体选择性地将双甘酯水解成单甘酯，在高水解率(50%以上)下，体外产生的1，2-sn-双甘油酯的对映体过量显著减少，甚至轻微逆转。这一发现可能解释了在十二指肠内消化的早期阶段体内观察到的二甘油酯低对映体过剩的原因，当时胰腺脂肪酶起主导作用，三酸甘油的水解率已经很高。另一方面，即使在较高的水解率下，从三油酸甘油酯产生的大量对映体过量的1，2-sn-二油酸酯仍然是体外胃脂酶的指纹图谱。胃脂肪酶指纹图谱在脂肪分解的胃内期和肠道晚期均可观察到。因此，这一特征被作为一个指标来确定胃和胰腺脂肪酶在体内脂肪分解过程中各自的作用。据我们所知，这是首次将立体选择性作为一种工具来区分体内降解同一底物的MIO酶的活性。(C)1997年，爱思唯尔科学有限公司。
The stereoselectivity of dog gastric and dog pancreatic lipases was investigated both in vitro, under simulated physiological conditions, and in vivo, during the digestion of a liquid test meal. In vitro it was observed that although both lipases had a stereopreference for the sn-3 position in triglycerides, it was about three times higher in the case of the gastric lipase. On the other hand, both lipases clearly showed a comparable enantioselectivity for the sn-1 position when a racemic diolein was used as the substrate. In the case of pancreatic lipase, the enantiomeric excess of 1,2-sn-diolein generated in vitro by the hydrolysis of triolein was found to decrease significantly, and even to be slightly reversed, at high rates of hydrolysis (above 50%) due to the further stereoselective hydrolysis of diglycerides into monoglycerides. This finding may explain the low enantiomeric excess of the diglycerides observed in vivo during the early phase of intraduodenal digestion when pancreatic lipase plays a predominant role and the rate of triolein hydrolysis is already high. On the other hand, a large enantiomeric excess of 1,2-sn-diolein generated from triolein was always the fingerprint of the gastric lipase in vitro even at high hydrolysis rates. This fingerprinting of gastric lipase was observed during both the intragastric phase and the late intestinal phase of lipolysis. This feature was therefore taken as an index to determine the respective roles of gastric and pancreatic lipases during in vivo lipolysis. To the best of our knowledge, this is the first time that stereoselectivity has been used as a tool to discriminate between the activities of mio enzymes hydrolyzing the same substrate in vivo. (C) 1997, Elsevier Science Ltd.