DIRECT BIOELECTROCATALYTIC REDUCTION OF HYDROGEN-PEROXIDE AT CHLOROPEROXIDASE MODIFIED GRAPHITE ELECTRODE

The electroreduction of hydrogen peroxide was studied at a chloroperoxidase-modified graphite electrode. The reduction of H2O2 starts at more negative potentials than 0.45 V versus SCE at pH 7.0. The steady-state reduction currents are greater at acidic pH values, and in the presence of chloride ions in solution. The apparent Michaelis-Menten constant and sensitivity were evaluated to be equal to 105 mu mol l(-1) and 1.3 mA l mol(-1) for the electrode responses to the H2O2 in 0.1 mol l(-1) phosphate buffer solution free of chloride ions. On the basis of these results direct electron transfer is postulated between the active site of chloroperoxidase and the graphite electrode.