F. Laveda et al., Proteolytic activation of latent Paraguaya peach PPO. Characterization of monophenolase activity, J AGR FOOD, 49(2), 2001, pp. 1003-1008
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.