Direct electrochemical oxidation of horseradish peroxidase: cyclic voltammetric and spectroelectrochemical studies

The direct, unmediated electrochemistry of horseradish. peroxidase (HRP) has been studied using a tin doped indium oxide coated glass working electrode at ambient pH. A well defined quasi-reversible cyclic voltammogram was obtained at high positive potentials corresponding to an E-1/2 of +700 mV vs. NHE. The cyanide complex of HRP also showed similar values of E-1/2, indicating formation of a pophyrin centred cation radical upon oxidation of the enzyme.