Purification of a laccase from fruiting bodies of the mushroom Pleurotus eryngii

A purification scheme involving ion exchange chromatography on diethylaminoethyl (DEAE) cellulose, carboxymethyl (CM) cellulose, and Q-Sepharose, followed by fast protein liquid chromatography–gel filtration on Superdex 75, was utilized to isolate a laccase from the fruiting bodies of the mushroom Pleurotus eryngii. The laccase was adsorbed on DEAE-cellulose and Q-Sepharose and unadsorbed on CM-cellulose. The molecular mass of the laccase in sodium dodecyl sulfate–polyacrylamide gel electrophoresis was 34 kDa. The laccase activity was maximal at 70°C and remained high at 80°C. High activity of the laccase was maintained at ph 3 to 5. The activity underwent an abrupt decline at pH 6 and 7 and was indiscernible at ph 8 and 9. The laccase exhibited an inhibitory activity toward HIV-1 reverse transcriptase with an IC50 of 2.2 μM. Its N-terminal sequence was dissimilar to those of laccase isoenzymes previously isolated from cultured mycelia of the same species.