LIPASE CONTROL BY PROTEIN INDUCED LIPID REORGANIZATION

胞外三酰甘油脂肪酶是重要的脂酶 消化和脂蛋白代谢。其中两个，胰腺 三酰甘油脂肪酶和脂蛋白脂肪酶的独特之处在于它们的 活性受低分子量蛋白质辅因子控制， 磷脂酶和载脂蛋白CII。这些辅因是 已知会吸收到这些脂肪酶所处的脂-水界面 与其他物质竞争的功能，如脂蛋白的表面 表面活性分子，如胆盐、白蛋白等 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，它们使 脂肪酶对表面的吸收，从而使其能够催化 存在于该界面中的脂类的水解性。我发现 这些辅因子蛋白之间的相互作用不是由一般的 表面作用，但表现出特异性。这种特殊性有利于他们的 脂解底物在界面上的吸附 偏爱基质脂类，如磷脂酰胆碱，并暗示 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 假设这一特性具有立体起源，并且 辅因子蛋白对底物的横向浓度调节 脂肪酶在界面和底物池中的吸附可及 到吸附的脂肪酶。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函数 吸附和铺展的单分子膜中的类脂结构 底物和基质脂质。对于选定的电影，亲和力和程度 脂肪酶吸附的效率和底物的吸附效率 脂肪酶也将被测量。脂肪酶吸附与吸附的相关性 具有脂类-辅因子相互作用数据的催化结果将提供 对第二种假设的检验。这些结果将增加我们的 了解这些和其他辅因子蛋白是如何形成的。 载脂蛋白AI，调节界面，酶催化的反应和 将增加我们对脂蛋白是如何 相互作用调节界面中的脂质侧向组织。

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.