Enzymological characterization of polyphenol oxidase (PPO) from taro was investigated using catechol as reaction substrate. The results showed that the optimal pH and temperature for this enzyme were 7.5 and 40 ℃, respectively. The total enzyme activity was almost lost after thermal treatment at 90 ℃for 2 min. The kinetics of PPO reaction was in accord with the Michaelis-menten equation, with Km and Vmax values of 0.0221 mol/L and 46.08 U/min, respectively. Four kinds of inhibitors had different effect on PPO with their inhibition effect order being of ascorbic acid>NaHSO3>L-Cysteine>citric acid. Mental ion of Sn2+ showed strong inhibitory effect on the enzyme. A13+, Cu2+, Mg2+, Ca2+ and Co2+ had certain inhibitory effects on the enzyme. The inhibition effects of Fe3+, Fe2+ and Mn2+ on enzyme were not significant. In addition, the enzyme can be activated by Zn2+.
