Fungal beta-glucosidases play a critical role in the last step of cellulose breakdown to glucose. The catalytic efficiency of beta-glucosidase can be inhibited by aqueous pH conditions. Engineering the substrate binding pocket by site-direct mutagenesis has implicated new approaches to overcome the pH sensitivity of beta-glucosidase. However, structural understanding of the pH-affected substrate binding environment remains poorly understood. Here we conducted molecular dynamics simulations of fully hydrated TrBgl2, a beta-glucosidase of <i>Trichoderma reesei</i>, equilibrated at its optimal pH (pH 6) and two unfavorable pHs (pH 5 and pH 7.5). We identified structural arrangement of specific residues that facilitated substrate escape from the catalytic site at pH 5 but locked the bound substrate in an unfavorable orientation at pH 7.5. For comparative analysis, we also performed simulations of a mutated TrBgl2 with previously demonstrated improved catalysis as a function of pH. We captured the responsible conformational changes in the engineered substrate binding pocket.

Insights from molecular dynamics simulations of substrate binding in a pH-affected fungal beta-glucosidase

256th National Meeting (2018)

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