Abstract: With electropolymerization of pyrrole, horse-radish peroxidase(HRP) was immobilized in the polypyrrole matrix to construct PP/HRPenzyme electrode, and its electrochemical behaviour was studied.In the deoxygenated phosphate buffer, the PP/HRPelectrode showed an accelerated H₂O₂ reduction, which was attributed to the direct electron transfer of the adduct of HRPwith H₂O₂.The simultaneous immobilization of HRPand K₄Fe(CN)₆ into the polypyrrole(PP) polymer and the electrochemical behaviour of as-formed enzyme electrodes were investigated.It was confirmed that, the existence of K₄Fe(CN)₆ in the polymer enabled the reduction potential of H₂O₂ to strongly shift to positive so that H₂O₂ could be detected at-0.05 V.The related process was explained in terms of indirect redox catalysis.

Key words: Horse-radish peroxidase, Enzyme electrode, Electrochemical immobilization, Bioelectrocatalytic reduction