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New Physiological Significance of Lipase

脂肪酶的新生理意义

基本信息

批准号：
11680638
负责人：
TSUJITA Takahiro
金额：
$ 0.45万
依托单位：
EHIME UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Various lipases (pancreatic lipase, caroxylester lipase, Pseudomonas fluorescens lipase and lipoprotein lipase) were purified on a large scale using thc PSLC chromatography system. The synthesis/hydrolysis of esters was studied in an aqueous solution using these purified lipases. When oleic acid and hexadecanol emulsified with gum araubic were incubated with these lipases at neutral pH, ester Was synthesized, in dose- and time-dependent manner, and the apparent equilibrium ratio of palmityl olcate/oleic acid was about 0.9/0.1. These lipase catalyzed the hydrolysis of palmityl oleate emulsified with gum arabic, and the apparent equilibrium ratio of palmityl oleate/free oleic acid also about 0.9/0.1. The equilibrium ratio was affected by the incubation pH and the alcohol chain length. When incubation pH was below pH 7.0 , the equilibrium ratio favored ester formation. The equilibrium ratio decreased sharply at alkaline pH (above pH 8.0). The ratio also deceased when fatty alcohols with acyl chains shorter than dodecanol were used. When trioleoylglycerol/hexadecanol emulsion was incubated with these lipases, palmityl oleate was synthesized in a dose- and time-dependent fashion. The lipase also synthesized retinyl ester from fatty acid and retinol, and diacylgycerol from fatty acid and monoacylglycerol. These results suggest that lipase catalyzes ester formation through an acyl-enzyme intermediate. The acyl-enzyme is deacylated by nucleophilic attack of various alcohols such as simple aliphatic alcohols, retinol, monoacylglycerol and water. Therefore, we might name the lipase "acyltransferase". These finding can be applied to understanding the mechanism of some water insoluble ester formations by lipase at various sites.

用PSLC层析系统对各种脂肪酶（胰脂肪酶、脂肪酸酯脂肪酶、荧光假单胞菌脂肪酶和脂蛋白脂肪酶）进行了大规模纯化。使用这些纯化的脂肪酶在水溶液中研究酯的合成/水解。在中性条件下，油酸和十六醇与阿拉伯树胶乳化后与这些脂肪酶共同孵育，均能合成酯，且呈剂量和时间依赖性，油酸棕榈酯/油酸的表观平衡比约为0.9/0.1。这些脂肪酶催化阿拉伯胶乳化的油酸棕榈酯水解，油酸棕榈酯/游离油酸的表观平衡比约为0.9/0.1。平衡比受孵育pH和醇链长度的影响。当孵育pH低于pH 7.0时，平衡比率有利于酯形成。在碱性条件下（pH 8.0以上），平衡比急剧下降。当使用酰基链短于十二烷醇的脂肪醇时，该比率也下降。当三油酰甘油/十六醇乳液与这些脂肪酶孵育时，油酸棕榈酯以剂量和时间依赖性的方式合成。该脂肪酶还能将脂肪酸和视黄醇合成视黄酯，并能将脂肪酸和甘油单酯合成甘油二酯。这些结果表明，脂肪酶催化酯的形成，通过酰基酶中间体。酰基酶通过各种醇如简单脂肪醇、视黄醇、单酰基甘油和水的亲核攻击而脱酰。因此，我们可以将脂肪酶命名为“酰基转移酶”。这些发现可用于理解脂肪酶在不同位点形成某些水不溶性酯的机理。