Gandía-Herrero Fernando, Jiménez-Atiénzar Mercedes, Cabanes Juana, García-Carmona Francisco, Escribano Josefa
Departamento de Bioquímica y Biología Molecular A, Unidad Docente de Biología, Facultad de Veterinaria, Universidad de Murcia, E-30100 Espinardo, Murcia, Spain.
Biol Chem. 2005 Jun;386(6):601-7. doi: 10.1515/BC.2005.070.
Polyphenol oxidase (PPO) was extracted from beet root, in both soluble and membrane fractions, and in both cases the enzyme was in a latent state. PPO from the membrane fraction showed no diphenolase activity unless it was activated by trypsin or sodium dodecyl sulfate (SDS). The kinetics of the activation process of latent PPO by trypsin was studied and the specific rate constant of active PPO formation, k 3 , showed a value of 0.03 s(-1). The protease-activated form showed a pH optimum (6.5) and kinetic properties identical to those of the SDS-activated enzyme. Evidence is provided for the existence of a common peptide responsible for the regulation of the activity of the enzyme by both proteolysis and SDS detergent. Formation of the active proteolyzate was followed by spectroscopic measurements, Western blotting and partially denaturing SDS-PAGE.
多酚氧化酶（PPO）从甜菜根中提取，存在于可溶性和膜部分，两种情况下该酶均处于潜伏状态。膜部分的PPO除非被胰蛋白酶或十二烷基硫酸钠（SDS）激活，否则不显示二酚酶活性。研究了胰蛋白酶对潜伏PPO的激活过程动力学，活性PPO形成的比速率常数k3的值为0.03 s(-1)。蛋白酶激活形式显示最适pH值为6.5，动力学性质与SDS激活的酶相同。有证据表明存在一种共同的肽，它通过蛋白水解和SDS去污剂来调节酶的活性。通过光谱测量、蛋白质印迹和部分变性SDS-PAGE跟踪活性蛋白水解产物的形成。
