Characterization of Polyphenol Oxidase and Peroxidase From Iranian Medlar (Mespilus germanica L.) Fruit

In this study, the crude protein extract containing PolyPhenolOxidase (PPO) and Peroxidases (POD) were extracted from medlar fruit (Mespilus germanica L.) grown in Golestan Province, Iran. POD and PPO activities were studied using guaiacol and catechol as substrates, respectively. The effect of pH, temperature and thermal stability, inhibitors and cations were investigated. Results showed that Vmax was higher for PPO compared to the POD. The optimum pHs for POD and PPO were obtained at 6.5 and 5.5, respectively. The optimum temperature for both enzymes was 35°C. The Iranian medlar POD was more thermal stable than the PPO. Ascorbic acid had the highest inhibitory effect on both enzymes. Ca^2+ and Zn^2+ had the highest decreasing and increasing effect on both enzymes.