Abstract:

Enzymatic characterization of polyphenol oxidase (PPO) from the leaves of Dysosma versipellis (Hance.) M.
Cheng was investigated using catechol as the reaction substrate. The results showed that the optimal substrate was catechol
at a concentration of 1.0 mol/L, and the optimal pH and temperature for this enzyme were 7.0 and 30 ℃, respectively. The
remaining activity of PPO was 11.92% after thermal treatment at 90 ℃ for 10 min. The kinetics of PPO reaction was fit to
the Michaelis-Menten equation, with Km and vmax value of 0.230 7 mol/L and 769.23 U/min, respectively. Different inhibitory
effects on PPO among ascorbic acid, glycine, EDTA and citric acid were observed. NaHSO3 showed stronger inhibitory
effect on PPO than Na2S2O3. The PPO could be activated by Al3+, Cu2+ and SDS. Ca2+ had certain inhibitory effect on the
PPO enzyme. In contrast, Mg2+, Fe2+ and Fe3+ had no significant effect on the enzyme activity (P < 0.05).

Key words: Dysosma versipellis (Hance.) M. Cheng, polyphenol oxidase, enzymatic properties