Toward computer-aided site-directed mutagenesis of enzymes.

A preliminary attempt to simulate the observed effect of a site-directed mutagenesis of rat trypsin gives encouraging results. The calculations reproduce in a semiquantitative way the observed change in the activation barrier of the rate-limiting step of amide hydrolysis. This result, which did not require any adjustable parameters, indicates that our method may provide a reliable basis for computer-aided enzyme design. In addition to the potentially practical value of the calculations, they provide important mechanistic information--that is, the change in the catalytic effect in trypsin appears to be almost exclusively due to the change in the electrostatic stabilization of the ionic configurations. This supports the view that electrostatic effects are the major factor in enzyme catalysis.