芋头多酚氧化酶的酶学性质研究

Enzymatic Properties of Taro Polyphenol Oxidase

以邻苯二酚为底物,采用分光光度法研究了芋头多酚氧化酶(PPO)的酶学特性。结果表明:芋头PPO的最适温度pH为7.5,最适温度为40℃;90℃高温处理2 min,可使酶完全失活;PPO催化的酶促褐变反应符合米氏动力学方程,相应动力学参数Km=0.0221mol/L,Vmax=46.08 U/min;4种抑制剂对PPO活性均有不同程度的抑制作用,抑制效果由强到弱顺序为:抗坏血酸>亚硫酸氢钠>L-半胱氨酸>柠檬酸;金属离子Sn2+对PPO活性具有较强的抑制作用,A13+、Cu2+、Mg2+、Ca2+和Co2+对PPO活性有一定的抑制作用,Zn2+对PPO活性具有激活作用,Fe3+、Fe2+和Mn2+对PPO活性几乎没有影响。

Enzymological characterization of polyphenol oxidase （PPO） from taro was investigated using catechol as reaction substrate The results showed that the optimal pH and temperature for this enzyme were 7.5 and 40℃, respectively. The total enzyme activity was almost lost after thermal treatment at 90 ℃ for 2 min. The kinetics of PPO reaction was in accord with the Michaelis-menten equation, with Km and Vmax values 0f0.0221 mol/L and 46.08 U/min, respectively. Four kinds of inhibitors had different effect on PPO with their inhibition effect order being of ascorbic acid〉NaHSO3〉L-Cysteine〉citric acid. Mental ion of Sn2＋ showed strong inhibitory effect on the enzyme. Al3＋, Cu2＋, M Ca2＋ and Co2＋ had certain inhibitory effects on the enzyme. The inhibition effects of Feat, Fe2＋ and Mn2＋ on enzyme were not significant. In addition, the enzyme can be activated by Zn2＋.