Laveda F, Núñez-Delicado E, García-Carmona F, Sánchez-Ferrer A
Department of Biochemistry and Molecular Biology-A, Faculty of Biology, University of Murcia, Campus de Espinardo, E-30071 Murcia, Spain.
J Agric Food Chem. 2001 Feb;49(2):1003-8. doi: 10.1021/jf001010m.
The kinetics of the activation process of latent peach PPO by trypsin was studied. By coupling this activation process to the oxidation of 4-tert-butylcatechol (TBC) to its corresponding quinone, it was possible to evaluate the specific rate constant of active PPO formation, k(3), which showed a value 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 time using p-cresol as substrate, and it showed the characteristic lag period of the kinetic mechanism of monophenols hydroxylation, which depended on the enzyme and substrate concentration, the pH and the presence of catalytic amounts of o-diphenol (4-methylcatechol). The enzyme activation constant, k(act), was 2 microM.
研究了胰蛋白酶对潜伏性桃多酚氧化酶（PPO）激活过程的动力学。通过将该激活过程与4-叔丁基邻苯二酚（TBC）氧化为其相应醌的过程相耦合，得以评估活性PPO形成的比速率常数k(3)，其值为0.04 s(-1)。潜伏性桃PPO的这种蛋白水解激活使我们首次能够以对甲酚为底物表征桃PPO的单酚酶活性，并且它显示出单酚羟基化动力学机制的特征性延迟期，该延迟期取决于酶和底物浓度、pH值以及催化量的邻二酚（4-甲基邻苯二酚）的存在。酶激活常数k(act)为2 microM。
