Electrochemical Characterization of the Laccase-Catalyzed Oxidation of 2,6-Dimethoxyphenol: an Insight into the Direct Electron Transfer by Enzyme and Enzyme-Mediator System

The oxidation process of 2,6-dimethoxyphenol (2,6-DMP) by laccase from Botryosphaeria rhodina MAMB-05 and the corresponding enzyme-mediator systems was studied using cyclic voltammetry (CV). The enzyme was classified as a high oxidation potential laccase (> 0.70) V vs. NHE) based on its Redox potential at different pHs. The cyclic voltammograms for 2,6-DMP (- 58.7 mV pH(-1)) showed that its oxidation potential decreased more significantly compared to the enzyme (- 50.2 mV pH(-1)) by varying the pH. The 2,2 '-azino-bis[3-ethyl-benzothiazoline-6-sulfonic acid] diammonium salt (ABTS) and 2,2,6,6-tetramethylpiperidine 1-oxyl radical (TEMPO) mediators were effectively oxidized by laccase from B. rhodina MAMB-05. The influence of laccase on the comproportionation of ABTS and the ionic step of the oxidation of TEMPO was also studied using CV. A higher potential difference was observed between laccase and the substrate, and correlated with higher enzyme activity. For the laccase-mediator systems, there was no clear correlation of potential difference between laccase and mediators with enzyme activity towards 2,6-DMP. This observation suggests that there are other limiting parameters for enzyme activity despite Redox potential difference, especially during ionic steps of the mechanism.

Automated summary

The study investigated the oxidation process of 2,6-dimethoxyphenol by laccase from Botryosphaeria rhodina MAMB-05 and the enzyme's classification as a high oxidation potential laccase based on different pH levels. Results showed that the substrates and mediators were effectively oxidized by the laccase, with the influence of laccase on the comproportionation of ABTS and the ionic step of the oxidation of TEMPO studied using cyclic voltammetry. The potential difference between laccase and the substrate was found to correlate with enzyme activity, while no clear correlation was observed between laccase and mediators with enzyme activity towards 2,6-DMP.