Brinkhuis J, Payens T A
Biochim Biophys Acta. 1985 Dec 20;832(3):331-6. doi: 10.1016/0167-4838(85)90267-5.
The proteolysis of micellar kappa-casein by rennet was followed by SDS-polyacrylamide gel-electrophoresis and the clotting of the para-kappa-casein formed by absorbance measurements. Up to a degree of proteolysis of about 0.4 the enzyme-inhibitor pepstatin A proved able to instantaneously stop the clotting. This effect is explained by the rapid condensation of monofunctional, monomeric and polymeric particles of para-kappa-casein. At higher degrees of proteolysis pepstatin was no longer able to completely block the polymerization. This is explained by the retardation of the condensation of the monofunctionals as their size grows larger. A kinetic analysis of the enzyme-controlled stage of the clotting process predicts that the system should gel at an early degree of proteolysis of about 0.07. The actual gel points occur at considerably higher degrees of proteolysis. This suggests that the enzymic attack of the polymeric inert kappa-casein particles is not completely at random. Primary micelles of kappa-casein, however, are degraded by random attack rather than by a 'catch-and-razor' mechanism.
用SDS - 聚丙烯酰胺凝胶电泳跟踪凝乳酶对胶束κ-酪蛋白的蛋白水解作用，并通过吸光度测量跟踪所形成的副κ-酪蛋白的凝结情况。在蛋白水解程度达到约0.4之前，酶抑制剂胃蛋白酶抑制剂A能够立即阻止凝结。这种效应可以通过副κ-酪蛋白的单功能、单体和聚合物颗粒的快速凝聚来解释。在更高的蛋白水解程度下，胃蛋白酶抑制剂不再能够完全阻止聚合。这可以通过随着单功能颗粒尺寸增大其凝聚的延迟来解释。对凝结过程中酶控制阶段的动力学分析预测，该系统在蛋白水解程度约为0.07的早期阶段就应该凝胶化。实际的凝胶化点出现在相当高的蛋白水解程度下。这表明聚合物惰性κ-酪蛋白颗粒的酶促攻击并非完全随机。然而，κ-酪蛋白的初级胶束是通过随机攻击而不是“捕获-切割”机制降解的。
