Enzymatic characteristics and inhibitors of polyphenol oxidase from Poria cocos

The enzyme activity of polyphenol oxidase( PPO) from Poria cocos was detected by spectrophotometry. The effects of pH value,temperature,substrate concentration and inhibitors on PPO activity were studied. The results indicated that the optimum pH value,temperature,and substrate concentration for PPO were 6. 5,35 ℃,and0. 06 mol /L,respectively. The kinetics of enzyme-catalyzed reaction of PPO complied with the law of Michaclis equation. The Kmand Vmaxwere 0. 024 4 mol /L and 121. 95 U /min,respectively. The activity of PPO was inhibited by sodium chloride,ascorbic acid,L-cysteine and citric acid. The inhibitory effects against PPO activity were increasing with the increasing concentrations. The order of inhibitors showing effects from strong to weak was as follows: L-L-cysteine,ascorbic acid,citric acid and sodium chloride.