Abstract: The poly-o-phenylenediamine membrane electrode containing horseradish peroxi-dase was prepared by means of the electrochemical immobilization of enzyme, and thevoltammetric behavior of the resulting enzyme electrode and its bioelectrocatalysis to hydro-gen peroxide reduction was studied.It was found that the direct electron tansfer between theenzyme and the polymer matrix takes place in the biocatalytic processes.For the newly pre-pared enzyme electrode, however, the oligomers, which are formed during the polymeriza-tion of o-phenylenediamine and then incorporated in the enzyme membrane, can play a role ofelectron transfer mediators to accelerate the regeneration of the oxidized enzyme.From thefitting of experimental current response curves, it can be found that the change in the regen-eration rates of the oxidized enzyme with the electrode potentials obeys apparantly the Tafelrelationship.The procedure in the measurement of kinetic parameters for enzyme reactionswas suggested.

Key words: Horseradish peroxidase, Poly-o-phenylenediamine, Bioelectrocatalysis, Amperometric enzyme electrodes