凝乳酶蛋白质工程的研究

Research progress of protein engineering for chymosin

由于微生物凝乳酶过多的非专一性水解和热稳定性高导致干酪产量降低和成熟中出现苦味。应用重组技术和蛋白质工程技术,使酶的一级结构发生可选择的和系统的变化,得到的蛋白质便具有所期望的功能特性。应用蛋白质工程对酶改性涉及到改变亚基结构和更换残基,改变酶的动力学参数和热稳定性,改变底物特异性以及最适pH等。

Chymosin used traditionally in cheese manufacture is an aspartic protease extracted from abomasum of suckling calves. The increasing world production of cheese, coupled with a decline in the number of slaughtered calves, has stimulated a search for alternative sources of chymosin. Microbe chymosin has been now used in large scale for cheesemaking. However, it has a much greater level of non-specific proteolytic activity and higher thermo-stability, leading to a reduction in yield and poor flavor development in cheese aging. Application of recombinant technology and protein engineering results in a selective and systemic alteration of primary structure of this enzyme and gives it more desirable functional properties. Modification of chymosin by protein engineering concerns changing subunit structure and residual group, affecting kinetic properties and ithemo-stability of enzyme,altering substrate specificity and optimum pH and so on.