Kinetics of direct and substrate-mediated electron transfer of versatile peroxidase-modified graphite electrodes

Electron transfer (ET) of versatile peroxidase (VP) was studied in the bioelectrocatalytic reduction reaction of H2O2 at peroxidase-modified graphite electrodes to obtain additional information on the kinetic characteristics of this novel ligninolytic peroxidase. Rotating disk electrodes (RDE) experiments were performed at 0 V (vs. SCE) in two different buffers (tartrate buffer, pH 5.0; and citrate buffer, pH 3.0). From measurements of the mediated and mediatorless currents of H2O2 reduction at the RDE, the percentage of VP molecules involved in direct ET (≈55%) was calculated. The peroxidase-modified electrodes were used for determination of the donor substrates in RDE mode, and the results were interpreted in terms of catalytic efficiencies.