Polyphenoloxidase (PPO) of Amasya apple was partially purified by (NH4)(2)SO4 precipitation and dialysis. The sample was used for characterization of the PPO. Optimum pH were 7.0, 9.0, 8.6 and 6.6 on substrates catechol, I-methyl catechol, pyrogallol and L-dopa respectively. Catechol was the most suitable for Amasya apple PPO. The optimum temperature for maximum PPO activity was 18 degrees C with catechol. Of seven inhibitors tested, the strongest was L-cysteine. Effectiveness of inhibitors increased in the order: thiourea, glutathione, beta-mercaptoethhanol, sodium cyanide, ascorbic acid, sodium metabisulfide, and L-cysteine. The K-M was 34 mM of catechol. The activation energy with catechol was 107 cal/mol. In electrophoretic separation, three isoenzymes were detected with both catechol and L-dopa substrates.