Molecular dynamics of an enzyme reaction: proton transfer in TIM

The initial proton transfer step in the reaction catalyzed by the enzyme triosephosphate isomerase is examined by activated dynamics simulations. The transmission coefficient, κ, which corrects the transition-state theory (TST) rate constant for recrossings of the activation barrier, is calculated to be 0.4, relative to the TST value of unity. Medium effects on the dynamics in the enzyme are compared with those on charge transfer reactions in solution.