Tuesday, May 3, 2011
Biomass recalcitrance against enzymatic deconstruction at the molecular level is related to the shape of cellulose microfibrils and the intrinsic work that an enzyme must conduct to decrystallize a cellulose chain from the crystal surface. Here we use molecular simulation to calculate the work that enzymes must conduct to decrystallize cellulose chains from cellulose Iβ, Iα, II, and IIII. From these results, we are able to elucidate the molecular-level differences between surface chains on the edges of these four different cellulose polymorphs. We then docked the Family 7 cellobiohydrolase (Cel7A) from Trichoderma reesei (or Hypocrea jecorina) on edges of cellulose microfibrils and conducted molecular dynamics simulations up to the microsecond time scale to determine the structure of the catalytically-active complex on a cellulose crystal. In addition, we investigated several mutations known experimentally to affect cellulose recognition and processivity of cellulose chains in Cel7A. These studies enable further understanding of cellulase action on insoluble, crystalline cellulose.