Partial properties of polyphenol oxidase in mango (Mangifera indica L. Cv. "Tainong") pulp

The properties of polyphenol oxidase (PPO, EC 1.14.18.1) from an extract of mango pulp were studied. PPO, with catechol as substrate, had an optimum pH at 7.0 and optimum temperature at 30C. PPO showed activity with dihydroxyphenols and trihydroxyphenols, but not with monohydroxyphenols. Kinetic parameters maximum velocity and Michaelis constant for PPO were 256.28 U/min and 6.30 mM with catechol, and 199.61 U/min and 47.81 mM with pyrogallol. The activity of PPO was well retained after heating the extract for 15 min at 50C, and 98% of the activity was lost after the extract was heated for 5 min at 80C. PPO was effectively inhibited by ascorbic acid as well as by beta-mercaptoethanol and L-cysteine, and was enhanced by sodium dodecyl sulfate.