Fungal Laccases with High and Medium Redox Potential: Is the T1 Center Potential a Key Characteristic of Catalytic Efficiency in Heterogeneous and Homogeneous Reactions?

Catalytic and bioelectrocatalytic properties of four white rot fungal laccases (, ThL; , CcL; , SmL; and , AfL) from different orthologous groups were comparatively studied in homogeneous reactions of electron donor substrate oxidation and in a heterogeneous reaction of dioxygen electroreduction. The ThL and CcL laccases belong to high-redox-potential enzymes (E = 780 mV), while the AfL and SmL laccases are medium-redox-potential enzymes (E = 620 and 650 mV). We evaluated the efficiency of laccases in mediatorless bioelectrocatalytic dioxygen reduction by the steady-state potential (E), onset potential (E), half-wave potential (E), and the slope of the linear segment of the polarization curve. A good correlation was observed between the T1 center potential of the laccases and their electrocatalytic characteristics; however, no correlation with the homogeneous reactions of electron donor substrates' oxidation was detected. The results obtained are discussed in the light of the known data on the three-dimensional structures of the laccases studied.