Enzymatic characterization of polyphenol oxidase(PPO) from Caozhou Chaenomeles sinensis was determined spectrophometrically using catechol as substrate.The results showed that the optimum pH and temperature for the enzymatic oxidation were 5.0 and 30℃,respectively.Thermal inactivation between 60 and 90℃ was observed to be biphasic with activation energy of 112.95 kJ / mol.The reaction kinetic for PPO-catalyzed browning was in accord with Michaelis-Menten equation,where the Michaelis constant Km and the maximum velocity value Vmax were 6.92 mmol / L and 769.23 U,respectively.NaHSO 3,ascorbic acid,L-cys,citric acid and EDTA-2Na significantly inhibited the PPO activity in the order of NaHSO 3 > ascorbic acid > L-cys > citric acid > EDTA-2Na.Na+and K+had no effect on PPO activity.The decreased PPO activity was observed in presence of Al3 +,Ba2 +and Cu2 +.Mg2 +,Mn2 + and Ca2 +activated PPO at lower concentration(1 mmol / L) while inhibited at higher concentration(10 mmol / L).