Heme Proteins and Model Systems

Abstract

This article describes mechanistic aspects of the active intermediate formation and a variety of reactions catalyzed by peroxidases. In two‐electron oxidations, a ferryl porphyrin π‐cation radical intermediate (the so‐called compound I) is generally involved, while one‐electron oxidation of substrates such as amines and phenols could proceed even when the active species is compound II, which is one‐electron reduced form of compound I (Fe IV O species). Many efforts have been made to utilize peroxidases as two‐electron oxidants rather than one‐electron oxidation cataysts. Site‐directed mutagenesis of peroxidases and myoglobin to construct highly efficient and enantioselective oxidation catalysts is an example of these efforts. In addition, random mutagenesis coupled with screening is a way of directed evolution to find biocatalysts suitable for desired oxidations. Chemical modification of amino acid residues and the heme prosthetic group is also an important strategy for the construction of enzymatic activities that are very different from those of the native enzymatic reactions.