鹰嘴豆β－半乳糖苷酶的研究──催化水解ONPG酶促反应动力学及其活性位的化学修饰

Studies on the β-Galactosidase from Gram──Gatalytic Reaction Kinetics of ONPG Hydrolysis and the Chemical Modification of Activity Sites

研究了鹰嘴豆发芽种子的β－半乳糖苷酶Ⅰ和β－半乳糖苷酶Ⅱ在催化水解邻硝基苯酚－β－Ｄ－半乳糖苷酶促反应中的催化性质和反应动力学，求得不同反应温度的米氏常数ＫＭ、最大反应速率ｒｍ和反应活化能Ｅａ等动力学参数，并以各种特征化学修饰剂对β－半乳糖苷酶Ⅰ中的活性基团进行了化学修饰。关联修饰情况与酶活性的关系，推知β－半乳糖苷酶Ⅰ中有色氨酸和巯基存在。它们是酶活性中心的组成基团，而该活性中心至少含有１个色氨酸和２个巯基，探讨了酶的活性位及其催化作用机理。

The catalytic properties of β-galactosidaseⅠand Ⅱpurified from gram germination seeds as ONPG hydrolysis catalysts were investigated.According to the MichaelisMenten mechanism of enzyme catalytic reaction,the kinetic parameters KM,rm and Ea of catalytic hydrolysis reaction of ONPG were measured.By using of various chemical dressing reagents for enzyme,we studied the function groups of β-galactosidaseⅠ.The relationship between the function groups and catalytic activity of enzyme revealed that hydrosulphonyl and tryptophan existed in β-galactosidase Ⅰand they were the composition groups in the active site of β-galactosidaseⅠfor the catalytic hydrolysis reaction of ONPG.