Direct electrochemistry and bioelectrocatalysis of horseradish peroxidase immobilized on active carbon

For the first time horseradish peroxidase (HRP) immobilized on the surface of active carbon powder modified at the surface of a glassy carbon electrode has been shown to undergo a direct quasi-reversible electrochemical reaction. Its formal potential, E0′, is −0.363 V in phosphate buffer solution (pH 6.8) at a scan rate of 100 mV/s and is almost independent of the scan rate in the range of 50–700 mV/s. The dependence of E0′ on the pH of the buffer solution indicated that the conversion of HRP–Fe(III)/HRP–Fe(II) is a one-electron-transfer reaction process coupled with one-proton-transfer. The experimental results also demonstrated that the immobilized HRP retained its bioelectrocatalytic activity to the reduction of H2O2. Furthermore, the HRP adsorbed on the surface of the active carbon powder can be stored at 4 °C for several months without any loss of the enzyme activity. The method presented for immobilizing HRP can be easily extended to immobilize and obtain the direct electrochemistry of other enzymes.