Catalysis by enzyme conformational change

An energy decomposition scheme is presented to elucidate the importance of the change of protein conformation substates to the reduction of activation barrier in an enzyme- catalyzed reaction. The analysis is illustrated by the reaction of orotidine 5'-monophosphate decarboxylase (ODCase), in which the catalyzed reaction is at least 10(17) faster than the spontaneous reaction. Analysis reveals that the enzyme conformation is more distorted in the reactant state than in the transition state. The energy released from conformational relaxation of the protein is the main source of the rate enhancement. The proposed mechanism is consistent with results from site-directed mutagenesis where mutations remote from the reaction center affect k(cat) but not K-M.