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A new lignin-degrading basidiomycete, strain PM1 (= CECT 2971), was isolated from the wastewater of a paper factory. The major ligninolytic activity detected in the basidiomycete PM1 culture supernatant was a phenoloxidase (laccase). This activity was produced constitutively in defined or complex media and appeared as two protein bands in native gel electrophoresis preparations. No enzyme induction was found after treatment with certain potential laccase inducers. Laccase I was purified to homogeneity by gel filtration chromatography, anion-exchange chromatography, and hydrophobicity chromatography. The enzyme is a monomeric glycoprotein containing 6.5% carbohydrate and having a molecular weight of 64,000. It has an isoelectric point of 3.6, it is stable in a pH range from 3 to 9, and its optimum pH is 4.5. The laccase optimal reaction temperature is 80 degrees C, the laccase is stable for 1 h at 60 …