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Understanding Biomass Deconstruction Enzymes for Biofuel Production

January 06, 2020

Challenge

Cellulase enzymes have the unique ability to deconstruct stubborn cellulose into soluble sugars, making them a biocatalyst of interest for biofuel research and production. Cellobiohydrolases (CBHs) are particularly promising enzymes, capable of freeing a great number of sugar molecules without dissociating from the cellulose substrate. This dissociation is rate limiting, but the molecular mechanism of this step is unknown, having not yet been discussed in literature or directly investigated.

Achievement

Using a combination of molecular simulation, structural biology, and biochemistry, NREL researchers and collaborators directly compared two previously proposed molecular mechanisms for CBH dissociation. Eagle's scale provided a platform for these simulations, allowing the team to compare competing hypothesized mechanisms for the very first time. In this study, the molecular dynamics engine NAMD provided a detailed dissociation mechanism for the cellulose-degrading enzyme TrCel7A. This study revealed the mechanism of CBH dissociation to be dethreading, in which the process of cellulose processivity is reversed.

Impact

With applications across nascent bioeconomy research, this study provides detailed knowledge that enables rational enzyme engineering for industrial use. These findings may help lower the cost of biomass deconstruction for upgrading to fuels and chemicals.

See the Proceedings of the National Academy of Sciences article The Dissociation Mechanism of
Processive Cellulases for more information.