The catalytic steps of a number of well-known enzymes have been perfected through evolution. The rates of the enzymatic reactions are thus determined by the rates of the diffusional encounter between the enzymes and their substrates. Provided that structural integrity is maintained, the diffusional encounter rate and thus the catalytic efficiency can be optimized by surface charge mutations near the active site. From past theoretical work, we have proposed that the electrostatic enhancement of protein-ligand or protein-protein association rates can be obtained from the following simple expression: ⁰ _B ⁰ _B...[ Read more ]

The catalytic steps of a number of well-known enzymes have been perfected through evolution. The rates of the enzymatic reactions are thus determined by the rates of the diffusional encounter between the enzymes and their substrates. Provided that structural integrity is maintained, the diffusional encounter rate and thus the catalytic efficiency can be optimized by surface charge mutations near the active site. From past theoretical work, we have proposed that the electrostatic enhancement of protein-ligand or protein-protein association rates can be obtained from the following simple expression:

k = k⁰{exp(-U/k_B XT)}

where k and k⁰ are the rate constants in the presence and absence of the interaction potential U, and (exp(- U/k_B x T)) is an average over the region in which the substrate can effectively bind to the enzyme to form a complex. In the present thesis project, this was used to study a number of enzyme-substrate and enzyme-inhibitor systems, including the binding of superoxide to superoxide dismutase and the association of barnase and barstar. Such studies have led to fundamental understanding on protein-ligand and protein-protein association and to designed enzymes that have optimized catalytic efficiency.