Electrocatalysis with a Glucose-Oxidase-immobilized Graphite Electrode

Glucose oxidase was immobilized on the surface of a graphite electrode by irreversible adsorption. An electrocatalytic steady-state current for the oxidation of D-glucose was observed using this electrode in the presence of p-benzoquinone as an electron transfer mediator. The electrocatalytic current at 0.5 V vs. SCE was analyzed as a function of the concentrations of D-glucose and p-benzoquinone, and the maximum current, I_s^max, and the Michaelis constants (K₁ and K₂ for D-glucose and p-benzoquinone, respectively) of the electrocatalysis were determined. The dependence of the current on the electrode potential, pH, and temperature was also investigated. The results indicate that the kinetics of the immobilized enzyme are essentially the same as those of the enzyme in the solubilized state. The effect of various electron transfer mediators on the electrocatalytic current was also examined and evaluated in terms of I_s^max, K₁, and K₂ values.