GOD was attached to glassy carbon electrodes by covalent binding with dicyclohexylcarbodiimide as an activator. The direct electron transfer between the immobilized enzyme and the electrode substrate was detected using both cyclic and differential pulse voltammetry, and considered as the redox transformation of FAD prosthetic groups in the holoenzyme. The apparent rate constant of electron transfer depends on the methods for enzyme immobilization, being roughly 1 s-1. The presence of Ag+ ions strongly interfered with electroredn. of the prosthetic groups; this may be related to the mechanism by which the ion inhibits enzymic activity of GOD. Ag+ inhibition can be released through treatment with EDTA or electrochem. treatment. GOD electrodes catalyze the reduction of oxygen and 1,4-benzoquinone, following an EC regenerative mechanism. The rate constant for the chem. reaction of benzoquinone with reduced GOD was measured, and the advantage of benzoquinone over oxygen as a mediator in bioelectrocatalysis was discussed.

Key words: REACTION KINETICS, ACTIVATING AGENT, ACTIVITY, ELECTRON TRANSFER, BENZOQUINONE, ELECTROCHEMICAL REACTION, CHEMICAL MODIFIED ELECTRODE, CARBODIIMIDE, BIOELECTROCHEMISTRY, ENZYME ELECTRODES