Crude enzyme extracts were prepared from Armillaria mellea (A. mellea), Lepista nuda (L. nuda) and Hypholoma fasciculare (H. fasciculare), which were harvested from the Liser High Plateau-Macka (Trabzon, Turkey). The crude polyphenol oxidase (PPO) extracts from each mushroom were highly active against 4-methylcatechol. Native polyacrylamide gel electrophoresis, stained by L-3,4-dihydroxyphenylalanine, showed the polyphenol oxidase potentials. The optimum pH value, for each enzyme, was 7.0. When enzyme extracts were incubated at pH 7.0 for 24 h at 4 degrees C, it was observed that L. nuda and H. fasciculare enzyme activities decreased by about 26% and 18%, respectively, but, A. mellea enzyme activity increased by about 11%. The temperature optima of A. mellea, L. nuda and H. fusciculare were, respectively, 30, 30 and 20 degrees C. Cr3+ and Cu2+ ions inhibited each activity. Also, sodium metabisulphite and ascorbic acid were strong inhibitors of the enzyme activities. (c) 2006 Elsevier Ltd. All rights reserved.