High electrochemical stability of hyperthermophilic archaeal multicopper enzyme adsorbed on gold electrodes compared to fungal laccase

Abstract

Multicopper enzymes (MCEs) have attracted significant recent attention for use as biocathodes in enzyme-catalyzed fuel cells, mostly to facilitate the four-electron reduction of oxygen to water. Au is highly biocompatible and does not exhibit a carbon-like tendency for toxicity. Especially, the development of an implant-type enzyme fuel cells with noble electrodes, such as those made of Au, can assist in resolving health issues. In the present research, a direct electron transfer (DET)-type reaction featuring a hyperthermophilic archaeon multicopper enzyme (McoP) and a Trametes sp. laccase (Lac) adsorbed on bare Au electrodes was investigated. Quartz crystal microbalance (QCM) analysis was used to examine the adsorption behavior of McoP and Lac on Au electrodes. The obtained results indicated that the adsorbed McoP on Au exhibited stability against a higher potential electric field (+0.8 V vs. Ag|AgCl) and showed stable bioelectrocatalysis for oxygen reduction (main production of H2O2 with two-electron reaction), compared with Lac. The electron transfer rate of the McoP at the Au electrode interface was evaluated to be 10 s−1. This finding could urgently contribute for developing biocathodes in enzyme-catalyzed fuel cell, especially implant-type enzymatic fuel cells.