Proteolytic modifications of laccase from Cerrena unicolor

Abstract

Laccase from the wood-degrading Cerrena unicolor FCL139 has been proved many times to be useful as a decolorizing enzyme, antibacterial agent, and important part of biosensors. In recent papers, there have been attempts to modify its structure and thereby alter its features and activity. In this work, proteolytic modification of laccase isoforms was performed. To achieve the goal, commercially available proteases: proteinase K, trypsin, pepsin, papain, and Rhizopus pepsin were applied. The results obtained proved that only proteinase K was able to digest laccase resulting in lowering its activities to only 7%. The other four proteases enhanced the activities of this multicopper oxidoreductase up to 140%. Proteolytic modification of laccase structure resulted also in enhancement of its prooxidative potential. Moreover, analysis of kinetic constants proved that Vmax of modified laccase increased over 2 times, the highest kcat (321.9±14.83L/s) was observed when analyzing laccase incubated with pepsin from Rhizopus. The electrochemical investigations of anodic peak (650mV vs Ag/AgCl), and cathodic peak (400mV) showed that pepsine-treated laccase had 2 times higher peaks than trypsin digested and four times higher than control experiment. Additionally, the remaining forms seem to inhibit proteolytic activities leaving even only 20% of its initial activity.