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How a single-point mutation in horseradish peroxidase markedly enhances enantioselectivity
Eugene Antipov1, Art E Cho, Alexander M Klibanov
1Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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 wild-type 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.
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