Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Product inhibition significantly impacts the efficiency of cellulose deconstruction by cellulase enzymes, but the reported product inhibition constants range over several orders of magnitude depending on the experimental conditions, and there is little consensus on the importance of this phenomenon. To provide insights into cellulase product inhibition, we examine the impact of product binding on both processive and nonprocessive cellulases by calculating the binding free energy of cellobiose to the catalytic domain of representative enzymes from glycoside hydrolase Families 6 and 7 using steered molecular dynamics and alchemical thermodynamics integration methods. Several point mutations on the key binding residues were also made computationally to study the binding free energy changes during the product expulsion process. We aim to engineer the cellulase enzymes to lower the binding free energy of cellobiose, thus accelerating the product expulsion process and improving the efficiency of biomass conversion.
References
1. L. Bu, G.T. Beckham, M.R. Shirts, M.R. Nimlos, W.S. Adney, M.E. Himmel, and M.F. Crowley. Probing carbohydrate product expulsion from a processive cellulase with multiple absolute binding free energy methods. J. Biol. Chem. 2011, 286: 18161-18169
2. L. Bu, M.R. Nimlos, M.R. Shirts, M.E. Himmel, and M.F. Crowley, and G.T. Beckham. Product inhibition varies dramatically between processive and nonprocessive cellulose enzymes. In preparation.
3. L. Bu, G.T. Beckham, C.M. Payne, D.W. Sammond, M.R. Shirts, M.R. Nimlos, M.E. Himmel, and M.F. Crowley. Comparison of steered molecular dynamics and thermodynamic integration for ligand binding: Application to product inhibition in a processive cellulose. In preparation.