Purification and characterization of extracellular laccase fromPleurotus ostreatus

Laccase (EC 1.10.3.2) from the culture filtrate of a strain of white rot basidiomycetePleurotus ostreatus was purified using DEAE-Toyopearl 650M and butyl-Toyopearl 650M column chromatographies and Superdex 75 HR 10/30 fast protein liquid chromatography. Molecular weight of the purified laccase was about 55,000, and the isoelectric point was 3.0. The optimum pH for enzyme activity was 6.5, and the optimum temperature was 50°C. This enzyme contained 7.4% sugar and two copper atoms per molecule. The substrate specificity was similar to those of other fungal laccases. Comparison of the N-terminal amino acid sequence of theP. ostreatus laccase with those fromPleurotus ostreatus Florida,Coriolus hirsutus, Phlebia radiata, basidiomycete PM1 (CECT 2971),Trametes villosa, Pycnoporus cinnabarinus, Ceriporiopsis subvermispora, andAgaricus bisporus showed 95, 65, 60, 55, 55, 55, 50, and 35% similarity, respectively, in the first 20 residues. No similarity in this region was detected with laccases fromNeurospora crassa, Aspergillus nidulans, andCryptococcus neoformans.