Proteolytic activation of latent Paraguaya peach PPO. Characterization of monophenolase activity

The kinetics of the activation process of latent peach PPO by trypsin was s tudied. By coupling this activation process to the oxidation of 4-tert-buty lcatechol (TBC) to its corresponding quinone, it was possible to evaluate t he specific rate constant of active PPO formation, k(3), which showed a val ue of 0.04 s(-1). This proteolytic activation of latent peach PPO permitted us to characterize the monophenolase activity of peach PPO for the first t ime using p-cresol as substrate, and it showed the characteristic lag perio d of the kinetic mechanism of monophenols hydroxylation, which depended on the enzyme and substrate concentration, the pH and the presence of catalyti c amounts of o-diphenol (4-methylcatechol). The enzyme activation constant, k(act), was 2 muM.