Banana Polyphenoloxidase. Preparation and Properties

Abstract

Banana polyphenoloxidase (PPO) was extracted from the fruit pulp with buffered detergent solution and further purified (10-12-fold) by chromatography on DEAE cellulose. The soluble enzyme was essentially free of endogenous activity and catalyzed the oxidation of diphenolic substrates including dopamine, DOPA, arterenol, catechol and chlorogenic acid. Dopamine, the primary substrate for browning reactions in the banana, had the lowest Michaelis constant (6.3 x 10-4 [image]). Banana PPO has optimum activity at pH 7.0 with dopamine as the substrate. The mechanism of dopamine oxidation appears to be analogous to that for the oxidation of DOPA by tyrosinase.