How carbohydrate-binding module affects the catalytic properties of endoglucanase.

The important role of Carbohydrate-binding module (CBM) in the cellulases catalytic activity has been widely studied. CBM3 showed highest affinity for cellulose substrate with 84.69 % adsorption rate among CBM1, CBM2, CBM3, and CBM4 in this study. How CBM affect the catalytic properties of GH5 endoglucanase III from Trichoderma viride (TvEG3) was systematically explored from two perspectives: the deletion of its own CBM(TvEG3dc) and the replacement of high substrate affinity CBM3 (TvEG3dcCBM3). Compared with TvEG3, TvEG3dc lost its binding ability on Avicel and filter paper, but its catalytic activity did not change significantly. The binding ability and catalytic activity of TvEG3dcCBM3 to Avicel increased 348.3 % and 372.51 % than that of TvEG3, respectively. The binding ability and catalytic activity of TvEG3dcCBM3 to filter paper decreased 51.7 % and 33.33 % than that of TvEG3, respectively. Further structural analysis of TvEG3, TvEG3dc, and TvEG3dcCBM3 revealed no changes in the positions and secondary structures of the key amino acids. These results demonstrated that its own CBM1 of TvEG3 did not affect its catalytic activity center, so it had no effect on its catalytic activity. But CBM3 changed the adsorption affinity for different substrates, which resulted in a change in the catalytic activity of the substrate.

An effective strategy for improving the specific activity and saccharification efficiency of cellulase by pre-incubation with phenolic acids.

This short communication analyzed the effects of lignin-derived phenolic acid compounds on cellulase. Vanillic acid, syringic acid, ferulic acid, and isovanillic acid improved cellulase specific activity and saccharification efficiency. In the enzymatic hydrolysis process, the promotion effect of phenolic acid was concentration-dependent. The effect of low concentration of phenolic acids (less than 5 mM) was negligible. After pre-incubating 1 g cellulase with 5 mmol phenolic acid, FPase-specific activity, CMCase-specific activity, and pNPGase-specific activity increased by 57.06%, 136.79%, and 110.61%, respectively. After digestion with pre-incubated cellulase, the saccharification efficiency of phosphoric acid-swollen cellulose increased by 45.13%. Pre-incubation with phenolic acid improved the saccharification efficiency of cellulase. It might be helpful to enhance the comprehensive utilization capacity of lignin-derived compounds.

Effect of carbohydrate binding modules alterations on catalytic activity of glycoside hydrolase family 6 exoglucanase from Chaetomium thermophilum to cellulose.

Exoglucanase (CBH) is the rate limiting enzyme in the process of cellulose degradation. The carbohydrate binding module (CBM) can improve the accessibility of cellulase to substrate, thereby promoting the enzymatic hydrolysis of cellulase. In this study, the influence of CBM on the properties of GH6 exoglucanase from Chaetomium thermophilum (CtCBH) is systematically explored from three perspectives: the fusion of exogenous CBM, the exogenous CBM replacement of its own CBM, and the deletion of its own CBM. The parental and reconstructed CtCBH presented the same optimum pH (6.0) and temperature (60 °C) for maximum activity. Fusion of exogenous CBM increased the binding capacity of CtCBH to Avicel by 8% and 9%, respectively, but it had no significant effect on its catalytic activity. The exogenous CBM replacement of its own CBM resulted in a 12% reduction in the binding ability of CtCBH to Avicel, and a 26% reduction in the catalytic activity of Avicel. The deletion of its own CBM significantly reduced the binding ability of CtCBH to Avicel by approximately 53%, but its catalytic activity was not obviously reduced. These observations suggest that binding ability of CBM is not necessary for the catalysis of CtCBH.