Purification and characterization of a novel laccase from the mushroom Pleurotus nebrodensis.

A novel laccase with a molecular mass of 64 kDa and the N-terminal sequence AIGPDDTINF was isolated from fresh fruiting bodies of the mushroom Pleurotus nebrodensis. The purification protocol comprised ion exchange chromatography on DEAE-cellulose, CM-cellulose, and Q-Sepharose, and gel filtration on Superdex 75. The laccase was adsorbed on DEAE-cellulose and Q-Sepharose, but not on CM-cellulose. It demonstrated an optimal temperature of 70°C. The enzyme activity increased steadily over the temperature range 20°C-70°C. There was only a slight reduction in activity at 80°C. However, all activity disappeared following exposure to 100°C for 10 minutes. The enzyme activity changed only slightly over the pH range 3-5, with the optimum at pH 5, but underwent a precipitous decline when the pH was elevated to 6, and was undetectable at pH 8 and pH 9.