Polyphenoloxidase (PPO) from Chinese pear ( Pyrus pyrifolia Nakai) was characterized using catechol as a substrate. PPO had a V(max) of 289.2 units/min and a K(m) of 3.8 mmol/L, which indicates that P. pyrifolia Nakai PPO has a great affinity for catechol. The catalyzing reaction velocity was proportional to the PPO concentration. The optimum pH and temperature for PPO activity were 4.5 and 45 degrees C, respectively. In addition, an investigation was made on the effect of high-pressure microfluidization of treatment pressure, treatment pass, and enzyme solution temperature on P. pyrifolia Nakai PPO. As the treatment pressure increased, the PPO relative activity was elevated from 100% untreated to 182.57% treated at 180 MPa. PPO relative activity was enhanced as the treatment pass increased. PPO solution temperature (25, 35, and 45 degrees C) had a significant effect on PPO relative activity when treated at 120 and 140 MPa.