MEDIATORLESS PEROXIDASE ELECTRODE AND PREPARATION OF BIENZYME SENSORS

Fungal peroxidase (from Arthromyces ramosus (ARP)), covalently immobilized on a graphite electrode, catalyzes the mediatorless reduction of hydrogen peroxide. In the pH range 4.92-7.00 the enzyme electrode steady-state potential reached a value of 995-908 mV (SHE) which is similar to the compound I and compound II single-electron reduction potentials. The enzyme electrode operated under diffusion-limiting conditions, and at hydrogen peroxidase concentrations lower than 2.5-mu-M the sensitivity was 0.84 A/M. A mediatorless ARP electrode was used to prepare glucose, methanol- and choline-sensitive bienzyme electrodes. The sensitivity of the electrodes based on covalently immobilized peroxidase and glucose oxidase (GO) or peroxidase and alcohol oxidase (AO) was 2.6 and 0.6 mA/M, respectively. The steady-state potential of the ARP/GO electrode was similar to that of the ARP electrode. The sensitivity of the peroxidase/choline oxidase (ChO) electrode with entrapped ChO was 0.48 mA/M. The pH optima of the ARP/GO and ARP/ChO electrodes were 6.0 and 8.7, respectively. ARP, ARP/GO and ARP/ChO electrodes retained their efficiency for 2-7 days; however, ARP/AO electrodes were less stable.