Abstract: Objective: To explore enzymatic properties of polyphenol oxidase (PPO) from kidney bean pods (Phaseolus vulgaris L. cv. Shuangqing). Methods: The optimal pH, temperature, substrate specificity and inhibitors of PPO were evaluated by polyacrylamide gel electrophoresis (PAGE). Results: The optima pH for PPO activity was 6.0. The PPO was relatively stable at 30 ℃ and inactivated at 80 ℃. Catechol was the optimal substrate for the enzyme. Its activity was inhibited by ascorbic acid, β-mercaptoethanol, glycine or L-cysteine. Moreover, the PPO activity was inhibited completely by 1.0 mmol/L β-mercaptoethanol or ascorbic acid; however, it was activated by copper dichloride and carbamide. Conclusion: High temperature, high pH and β-mercaptoethanol or ascorbic acid can inhibit the activity of the PPO enzyme.

Key words: polyphenol oxidase, polyphenol property, polyacrylamide gel electrophoresis (PAGE) , kidney bean pod