Fig. 1

Schematic diagram of laccase catalytic cycle, adapted from Baldrian [10]. The laccase substrate is oxidized by Cu1, involving the loss of a single electron and the formation of a free radical, which may undergo further oxidation or nonenzymatic hydration, disproportionation and polymerization. Reduction of Cu1 is rate-limiting in the catalytic process. The extracted electron is transferred through highly conserved His-Cys-His motif to the trinuclear copper cluster, where molecular oxygen is reduced to water. The reduction of one molecule of oxygen to two molecules of water is accompanied by oxidation of four molecules of substrate