EFFECTS OF GLUCOSE AND MANNOSE DERIVED FROM BIOMASS DEGRADATION ON CEL7A INHIBITION

The enzymatic breakdown of lignocellulosic biomass is crucial for producing biofuels and biochemicals, offering a sustainable alternative to fossil fuels. Cel7A, a cellobiohydrolase, is one of the most efficient cellulases involved in this process, catalyzing the hydrolysis of cellulose into cellobiose. However, sugar products released during biomass degradation, such as glucose and mannose, are known inhibitors of Cel7A, reducing its catalytic efficiency and limiting overall biomass conversion.^1,2 Inhibition has been shown to occur via interactions with both the catalytic domain (CD) and the carbohydrate-binding module (CBM) of the enzyme. The CBM facilitates adsorption of the enzyme to the cellulose surface, a prerequisite for effective cellulose hydrolysis by Cel7A. However, soluble sugars compete with cellulose for CBM binding sites, reducing the enzyme’s processivity and hydrolytic efficiency.² In this study, we investigated the solvation structures of the CBM in glucose and mannose solutions using molecular dynamics simulations. Solvation patterns were characterized through Minimum-Distance Distribution Functions and Kirkwood–Buff theory, computed with the ComplexMixtures.jl package.³ Results from 15 replicas of each system at six different concentrations show that glucose and mannose are excluded from the protein surface, but exhibit strong interactions with the cellulose-binding face. This suggests a mechanism by which sugar molecules compete with cellulose for CBM binding. Furthermore, our results reveal a concentration-dependent solvation pattern, where the CBM is solvated by glucose at 1 mol L^-1. Together, these findings provide new insights into the mechanisms of sugar-mediated inhibition during cellulose hydrolysis.