In silico studies disclose the underlying link between binding affinity and redox potential in laccase isoforms.

Laccases are copper-containing enzymes belonging to the family of multicopper oxidases (MCOs). All MCOs use molecular oxygen to oxidize a wide range of organic compounds by radical catalysis. One of the key fundamental properties of laccases is having high or low redox potentials depending on the active site organization. Several experimental studies have been done to rationalize the high and low redox potential laccases (LRPL), however, molecular understanding is still lacking. In this work, we explored the proteomic profile of laccases produced in the fungal cultures, specifically induced with lignocellulosic biomass such as rice straw. This study was undertaken to explain the differences in the high redox and low redox potential values of different laccases using in-silico approaches. Proteomic profiling and structural and sequence analysis revealed a low level of similarity among them. Docking analyses and molecular dynamics simulation analysis revealed that high redox potential laccases (HRPL) are having good binding affinity compared to low or medium redox potential laccases (MRPL). The stability of these complexes was further analyzed based on reactive distances, active site volume comparison and a number of tunnel formations that were observed to be significantly higher for HRPL. Our results indicate that the number of tunnel formations calculated from the simulation's trajectories and available water molecules at the T3 site directly correlates with the laccases' redox potentials. This study will be helpful and provide valuable inputs for the designing of new laccases to improve lignin degradation. Communicated by Ramaswamy H. Sarma.