The result of PAGE for laccase crude extract showed that three kinds of isoenzymes exist in the Auricularia polytricha AP4. The molecular weight of the three isoenzymes was determined by Native SDS-PAGE: LacA (110kD), LacB (84kD), LacC (65kD). The LacB was purified from AP4 by ammonium sulphate fractionation, DEAE sephrase fast flow chromatography.The optimum pH and temperature for LacB activity were 4.0℃ and 30℃, respectively. The LacB catalyzed the oxidation of ABTS with a Michaelis constant of 6.64× ...