Improvement of catalytic performance of endoglucanase CgEndo from Colletotrichum graminicola by site-directed mutagenesis

Abstract

In order to improve the catalytic efficiency of cellulase for more effective utilization of lignocellulose, a novel endoglucanase (CgEndo) from Colletotrichum graminicola was expressed by Pichia pastoris X33 and modified by site-directed mutagenesis. Two mutants, Y63S and N20D/S113T, with 62.31% and 57.14% increased enzyme activities were obtained, respectively. On this basis, their biochemical properties, kinetic parameters, structural information as well as the application in biomass degradation were investigated and compared with the wild-type CgEngo. The results indicated that the mutation Y63S and N20D/S113T resulted in an improvement of proximity between enzyme and substrate through conformational changes of the catalytic region, which might contribute to the higher enzyme activities and catalysis efficiency (Kcat/Km) of Y63S and N20D/S113T. These findings laid important foundation for the further engineering of this endoglucanase and practical application in efficient degradation of cellulosic biomass in nature.