Electrochemical evaluation of electron transfer kinetics of high and low redox potential laccases on gold electrode surface

• Published in: Electrochimica acta Vol. 56; no. 2; pp. 817 - 827
• Main Authors: Frasconi, Marco, Boer, Harry, Koivula, Anu, Mazzei, Franco
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 30-12-2010; Elsevier
• Subjects: Applied sciences; Corrosion inhibitors; Direct electron transfer; Electrode potentials; Electrodes; Electron transfer; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Gold; Gold electrode; Inhibition; Laccase; Reaction kinetics; Voltammetry; Direct electron transfer; Voltammetry; Gold electrode; Laccase; Coriolus versicolor; Electron transfer; Basidiomycota; Fungi; Chemical reduction; Electrocatalysis; Biochemical fuel cell; Rhus verniciflua; Dicotyledones; Angiospermae; Electrochemical reaction; Anacardiaceae; Gold; Oxygen; Enzyme; Transition metal; Enzyme electrode; Electrochemical properties; Spermatophyta; Oxidoreductases; Kinetics; Immobilized enzyme
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2010.09.056

Laccases and other multicopper oxidases are reported to be able to carry out direct electron transfer reactions when immobilized onto electrode surface. This allows detailed research of their electron transfer mechanisms. We have recently characterized the kinetic properties of four laccases in homogenous solution and immobilized onto an electrode surface with respect to a set of different redox mediators. In this paper we report the direct electron transfer of four purified laccases from
Trametes hirsuta (ThL),
Trametes versicolor (TvL),
Melanocarpus albomyces (r-MaL) and
Rhus vernicifera (RvL), by trapping the proteins within an electrochemically inert polymer of tributylmethyl phosphonium chloride coating a gold electrode surface. In particular, we have characterized the steps involved in the laccases electron transfer mechanism as well as the factors limiting each step. During the voltammetric experiments, non-turnover Faradic signals with midpoint potential of about 790 and 400
mV were observed for high potential laccases, ThL and TvL, corresponding to redox transformations of the T1 site and the T2/T3 cluster of the enzyme, respectively, whereas low redox potential laccases r-MaL and RvL shown a redox couple with a midpoint potential around 400
mV. The electrocatalytic properties of these laccase modified electrodes for the reduction of oxygen have been evaluated demonstrating significative direct electron transfer kinetics. The biocatalytic activity of laccases was also monitored in the presence of a well known inhibitor, sodium azide. On the basis of the experimental results, a hypothesis about the electronic pathway for intramolecular electron transfer characterizing laccases has been proposed.