Jain M K, Jahagirdar D V
Biochim Biophys Acta. 1985 Apr 11;814(2):313-8. doi: 10.1016/0005-2736(85)90450-x.
Action of pig pancreatic phospholipase A2 on the ternary codispersions of diacylphosphatidylcholine, 1-acyllysophosphatidylcholine and fatty acids is examined. The binding and kinetic constants are found to be the same under a variety of conditions. These parameters and the catalytic turnover number change with the phase-transition temperature of the ternary codispersions, and optimal binding, kinetic and catalytic constants are seen in the phase-transition range where an equilibrium exists between laterally separated phases. The effect of changing the structure of any of the three components is also via a change in the phase-transition temperature of their ternary codispersions. These observations suggest that the binding of pig pancreatic phospholipase A2 to the defect sites on the substrate interface determines the substrate concentration dependence of the initial rate of hydrolysis, and the catalytic turnover by the bound enzyme also depends upon the phase state of the bilayer. An additive-induced stabilization of the defects in the substrate bilayer is postulated to account for the enhanced binding of the enzyme to the bilayer.
研究了猪胰磷脂酶A2对二酰基磷脂酰胆碱、1-酰基溶血磷脂酰胆碱和脂肪酸三元共分散体系的作用。发现在各种条件下，结合常数和动力学常数是相同的。这些参数以及催化周转数随三元共分散体系的相变温度而变化，并且在横向分离相之间存在平衡的相变范围内可以看到最佳的结合、动力学和催化常数。改变三种组分中任何一种的结构所产生的影响也是通过改变其三元共分散体系的相变温度来实现的。这些观察结果表明，猪胰磷脂酶A2与底物界面上的缺陷位点的结合决定了水解初始速率对底物浓度的依赖性，并且结合酶的催化周转也取决于双层的相态。推测添加剂诱导的底物双层中缺陷的稳定作用可以解释酶与双层结合的增强。
