以茯苓为供试材料,采用分光光度计法测定多酚氧化酶(PPO)活力,研究pH值、温度、底物浓度以及抑制剂等因素对茯苓PPO活性的影响。结果表明,茯苓PPO最适pH值为6.5,最适温度为35℃,最适底物浓度为0.06 mol/L。PPO酶促反应动力学符合米氏方程,动力学参数Km=0.024 4 mol/L,Vmax=121.95 U/min。NaCl、抗坏血酸、L-半胱氨酸和柠檬酸溶液对茯苓PPO均有抑制作用,随着质量浓度的升高,抑制效果越好;相同质量浓度下,L-半胱氨酸抑制作用最强,其次是抗坏血酸和柠檬酸,最后是NaCl。

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.