Recent advances in understanding the mechanism of action of CBH I cellulase through advanced MD simulations

With the depletion of fossil fuels and related increases in oil price, bio fuels become ever more attractive as an alternative source of energy. The production of ethanol from lignocellulose has been identified as a vital step in reducing our nation's dependence on foreign oil. The enzymatic conversion of cellulose to glucose for use in fermentation offers an attractive solution for large scale bio ethanol production. However, the turnover rates of natural cellulases are too low to be commercially viable. A detailed understanding of the mechanisms of action of these cellulases would offer the possibility for improving their efficiency and ultimately reducing bio ethanol production costs while at the same time unlocking an abundant and renewable feed stock. Due to the insolubility of cellulose one of the most promising families of cellulases are the processive enzymes which successively hydrolyze linkages in a single chain. We have employed a range of advanced molecular dynamics techniques, including umbrella sampling, targeted MD and replica exchange, to gain insight into the mechanism of action of the CBH I cellulase enzyme (Cel7A) from T. reesei. By focusing on individual domains of the enzyme we have been able to isolate specific properties of this enzyme including insights into how the binding domain identifies the cellulose substrate and subsequently a broken cellulose strand as well as how the energetic potential within the catalytic tunnel varies as a function of the chain position. We present here recent results from these simulations including the identification of a potential induced fit mechanism between the binding module and the cellulose substrate.