Characterization of polyphenol oxidase from Cape gooseberry (Physalis peruviana L.) fruit

• Biochemical properties of PPO from Cape gooseberry were analyzed.
• The optimal pH and temperature for three substrates were determined.
• The Cape gooseberry PPO activity decreased over time with fruit ripening.
• Different substrates were analyzed to determine their affinities with PPO.
• PPO activity was strongly inactivated by quercetin and ascorbic acid.

Cape gooseberry (Physalis peruviana) is an exotic fruit highly valued, however it is a very rich source of polyphenol oxidase (PPO). In this study, Cape gooseberry PPO was isolated and biochemically characterized. The enzyme was extracted and purified using acetone and aqueous two-phase systems. The data indicated that PPO had the highest substrate affinity for chlorogenic acid, 4-methylcatechol and catechol. Chlorogenic acid was the most suitable substrate (Km = 0.56 ± 0.07 mM and Vmax = 53.15 ± 2.03 UPPO mL−1 min−1). The optimal pH values were 5.5 for catechol and 4-methylcatechol and 5.0 for chlorogenic acid. Optimal temperatures were 40 °C for catechol, 25 °C for 4-methylcatechol and 20 °C for chlorogenic acid. In inhibition tests, the most potent inhibitor was found to be ascorbic acid followed by l-cysteine and quercetin. This study shows possible treatments that can be implemented during the processing of Cape gooseberry fruits to prevent browning.