Abstract: Polyphenoloxidase (ppo) was extracted from Thompson seedless grape grown in Xingjiang and its characteristics were studied. The optimal temperature and pH were 20℃ and 7.0 respectively, but 45% activity was seen at pH 3.0. The Michaelis equation was V=0.091[S]/(54.01+[S]).It followed the reaction of point-kinetics. The PPO showed higher affinity toward the catechin and caffeic acid than toward the chlorogenic acid and catechol.

Key words: Thompson seedless grape Polyphenoloxidase Characteristic