Purification and Characterization of White Laccase from the White-rot Fungus Panus conchatus

Laccase is a kind of polyphenol oxidase having potential in applications for pulp bleaching, waste water treatment in mills, and removal of phenols in the food industry. The normal laccase from fungus or bacterial contains four copper atoms per protein molecular, imparting a blue color. Here it is reported that a white laccase is produced by a white rot fungus Panus conchatus from its solid-state fermentation. The activity center of this laccase is Cu2FeZn, which lacks the typical type-1 blue copper color. The polyacrylamide gel electrophoresis of purified laccase showed a main polypeptide with a molecular weight of about 60 kDa. Laccase substrate 2,6-dimethoxylphenol and others, such as syringaldazine, otolidine, and ABTS, were readily oxidized, among which the Km for syringaldazine was the highest. The isoelectric point of this enzyme was 3.6 and it was stable at temperatures below 45 °C over a wide range of pH (4-12).