Kitano H, Maeda Y, Okubo T
Department of Polymer Chemistry, Kyoto University, Japan.
Biophys Chem. 1989 Mar;33(1):47-54. doi: 10.1016/0301-4622(89)80006-7.
The dimeric association process of alpha-chymotrypsin has been studied with the aid of a stopped-flow spectrophotometer at various temperatures and pH values. From the temperature dependences of the forward reaction rate constant (kf) and the equilibrium dimerization constant (KD), the reaction system observed here is concluded to be entropy-driven. The increase in entropy can be attributed to the release of water molecules from both the active site and the surface part of the protein molecule during the course of dimerization. From the pH dependences of the reaction rate constants and the equilibrium constant, the reaction is concluded to depend strongly on the dissociations of the site between the carboxyl group of the aspartic acid and imidazolyl group of the histidine residues (in the higher pH region), and the site between the imidazolyl group of the histidine and the carboxyl group of the tyrosine residue (in the lower pH region), respectively.
借助停流分光光度计，在不同温度和pH值条件下研究了α-糜蛋白酶的二聚体缔合过程。根据正向反应速率常数（kf）和平衡二聚化常数（KD）对温度的依赖性，得出此处观察到的反应体系是由熵驱动的结论。熵的增加可归因于二聚化过程中水分子从蛋白质分子的活性位点和表面部分释放出来。根据反应速率常数和平衡常数对pH的依赖性，得出该反应分别强烈依赖于天冬氨酸羧基与组氨酸残基咪唑基之间的位点（在较高pH区域）以及组氨酸咪唑基与酪氨酸残基羧基之间的位点（在较低pH区域）的解离。
