Site-directed Mutagenesis and Effects on the Enzymatic Properties of Subtilisin E
枯草蛋白酶E的定点突变及其对酶性质的影响

Site\|directed mutagenesis was used to investigate the effects of S221C/P225A,N118S/S221C/P225A,D60N/N118S/S221C/P225A and Q103R/N118S/S221C/P225A mutations on the properties of Subtilisin E.It was found that S221C/P225A mutant is 73 000\|fold decreased in amidase activity than subtilisin E and 3\|fold increased than subtiligase in the ratio of esterase/amidase;N118S/S221C/P225A mutant has 3\^6\|fold and 15\|fold decreased in amidase and esterase activity respectively and as a result,it has a 4\|fold lower in the ratio of amidase/esterase than S221C/P225A mutant;Although it has no effect on the esterase activity,D60N/N118S/S221C/P225A mutant enhanced its ratio of amidase/esterase by 15 fold,3\^3\|fold and 10\^3 fold compared to N118S/S221C/P225A mutant,S221C/P225A mutant and subtiligase respectively;Q103R/N118S/S221C/P225A mutant,however,has a 5\|fold enhanced in the amidase activity and 55\|fold and 1000\|fold decrease in the esterase activity and the ratio of esterase/amidase compared to N118S/S221C/P225A.