A laccase with a molecular mass of 67 kDa and inhibitory activity toward HIV-1 reverse transcriptase (IC50 = 7.5 microM) was isolated from fresh fruiting bodies of the Lentinus edodes (Shiitake mushroom). Its characteristics were compared with those of laccases from cultured mushroom mycelia reported earlier. The laccase was unadsorbed on DEAE-cellulose, Affi-gel blue gel and CM-cellulose, but was adsorbed on Con A-Sepharose. About 50-fold purification was achieved with a 19.2% yield of the

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... me. The activity of the enzyme increased steadily from 20 degrees C to 70 degreesC. The activity disappeared after exposure to the boiling temperature for 10 min. Its optimal pH was 4 and very little enzyme activity remained at and above pH 10. The laccase inhibited HIV-1 reverse transcriptase with an IC50 of 7.5 microM, but did not demonstrate any antifungal or anti-proliferative activity.