LIPASE CONTROL BY PROTEIN INDUCED LIPID REORGANIZATION

胞外三酰甘油脂肪酶是重要的脂类代谢酶 消化和脂蛋白代谢。 两个这个，胰腺的 甘油三酯脂肪酶和脂蛋白脂肪酶是独特的，因为它们 活性由低分子量蛋白质辅因子控制， 辅脂酶和载脂蛋白CII。 这些辅助因子是 已知这些脂肪酶吸收到脂-水界面， 功能，例如脂蛋白的表面，与其他脂蛋白竞争。 表面活性分子，例如胆汁盐、白蛋白和其他 载脂蛋白 每个辅因子也参与蛋白质-蛋白质 与其各自的脂肪酶相互作用。 通过这种方式， 将脂肪酶吸附到表面，从而使其催化 存在于该界面中的脂质的水解。我发现 这些辅因子蛋白的相互作用不是由一般的 表面活性，但表现出特异性。这种特殊性有利于他们 吸附到含有脂解底物的界面， 对磷脂酰胆碱等基质脂质的偏好，并意味着 这些底物将集中在辅因子附近 在界面的平面上。 该项目的目的是测试 假设这种特异性具有空间起源， 辅因子蛋白对底物侧向浓度的调节 脂肪酶吸附到界面和底物池中 吸附脂肪酶。 空间位阻假说将通过以下方式进行检验： 测量脂质-辅因子相互作用的强度作为以下的函数： 吸附和铺展的单分子膜中的脂质结构， 底物和基质脂质。 对于选定的膜， 脂肪酶的吸附和底物的可用性吸附 还将测量脂肪酶。 脂肪酶吸附与 催化结果与脂质辅因子相互作用数据将提供 对第二个假设的检验。 这些成果将提高我们的 了解这些和其他辅因子蛋白，例如， 载脂蛋白AI，调节界面，酶催化反应， 将增加我们对脂质-蛋白质 相互作用调节界面中的脂质横向组织。

Extracellular triacylglycerol lipases are important enzymes of lipid digestion and lipoprotein metabolism. Two of these, pancreatic triacylglycerol lipase and lipoprotein lipase, are unique in that their activities are controlled by low molecular weight protein cofactors, colipase and apolipoprotein CII, respectively. These cofactors are known to absorb to the lipid-water interfaces at which these lipases function, e.g. the surface of a lipoprotein, in competition with other surface-active molecules, e.g. bile salts, albumin and other apolipoproteins. Each cofactor also engages in protein-protein interactions with its respective lipase. In this way they enable the absorption of the lipase to the surface and, hence, allow it to catalyze the hydrolysis of lipids residing in that interface. I have discovered that the interaction of these cofactor proteins is not driven by general surfactancy but exhibits specificity. This specificity favors their adsorption to interfaces containing the substrates of lipolysis in preference to matrix lipids, like phosphatidylcholine, and implies that these substrates will be concentrated in the vicinity of the cofactor in the plane of the interface. The aims of this project are to test the hypotheses that this specificity has a steric origin and that the lateral concentration of substrate by cofactor protein regulates both lipase adsorption to the interface and the pool of substrate accessible to adsorbed lipase. The steric hindrance hypothesis will be tested by measuring the strength of lipid-cofactor interactions as a function of lipid structure in adsorbed and spread monomolecular films containing substrates and matrix lipid. For selected films the affinity and extent of lipase adsorption and the availability of substrate to adsorbed lipase will also be measured. Correlation of the lipase adsorption and catalysis results with the lipid-cofactor interaction data will provide a test of the second hypothesis. These results will increase our understanding of how these and other cofactor proteins, e.g. apolipoprotein AI, regulate interfacial, enzyme-catalyzed reactions and will increase our fundamental understanding of how lipid-protein interactions regulate lipid lateral organization in interfaces.