Structural and mechanistic fundamentals for designing of cellulases

A mutant β-glucosidase increases the rate of the cellulose enzymatic hydrolysis

The enzymatic hydrolysis of cellulose and lignocellulosic materials is marked by a rate decrease along the reaction time. Cellobiohydrolase slow dissociation from the substrate and its inhibition by the cellobiose produced are relevant factors associated to the rate decrease. In that sense, addition of β-glucosidases to the enzyme cocktails employed in cellulose enzymatic hydrolysis not only produces glucose as final product but also reduces the cellobiohydrolase inhibition by cellobiose. The digestive β-glucosidase GH1 from the fall armyworm Spodoptera frugiperda, hereafter called Sfβgly, containing the mutation L428V showed an increased k_cat for cellobiose hydrolysis. In comparison to assays conducted with the wild-type Sfβgly and cellobiohydrolase TrCel7A, the presence of the mutant L428V increased in 5 fold the initial rate of crystalline cellulose hydrolysis and reduced to one quarter the time needed to TrCel7A produce the maximum glucose yield. As our results show that mutant L428V complement the action of TrCel7A, the introduction of the equivalent replacement in β-glucosidases is a promising strategy to reduce costs in the enzymatic hydrolysis of lignocellulosic materials.