How a Single-Point Mutation in Horseradish Peroxidase Markedly Enhances Enantioselectivity

Abstract

The effect of all possible mutations at position 178 on the enantioselectivity, of yeast surface-bound horseradish peroxidase (HRP) toward chiral phenols has been investigated. In contrast to their wildtype predecessor, most HRP mutants are enantioselective, with the Arg178Glu variant exhibiting the greatest, 25-fold, (S)/(R) preference. Using kinetic analysis of enzymatic oxidation of various substrate analogues and molecular modeling of enzyme-substrate complexes, this enantioselectivity enhancement is attributed to changes in the transition state energy due to electrostatic repulsion between the carboxylates of the enzyme's Glu178 and the substrate's (R)-enantiomer.