毛酸浆多酚氧化酶的酶学特性研究

Study on Enzymatic Characteristics of Polyphenol Oxidase from Physalis pubescens L.

以毛酸浆中多酚氧化酶(PPO)为研究对象,采用分光光度法在420nm处对其酶学特性进行研究。结果表明,毛酸浆PPO的底物邻苯二酚的最适质量分数为0.04%;最适pH为7.0;最适温度为35℃;100℃处理2min,可使酶完全失活;PPO催化的酶促褐变反应动力学符合米氏方程,动力学参数为Km=0.025mol/L,Vmax=125U/min;抗坏血酸、柠檬酸、L-半胱氨酸和亚硫酸钠对PPO酶活性的抑制作用均随浓度的增大而加强,抑制能力由强到弱依次为:抗坏血酸>柠檬酸>L-半胱氨酸>EDTA>亚硫酸氢钠。

The enzymatic characteristics of polyphenol oxidase（PPO） from Physalis pubes-cens L.was studied by spectrophotometer at 420nm. The results showed that the PPO enzyme had the highest activity at pH 7.0 and 35 ℃ and the enzyme activity would been inactivated completely after exposure to 100 ℃ for 2min. The kinetics of enzyme-catalyzed reaction of PPO was in accord with Michaelis-Menten equation,with Kmand Vmax values of 0.025mol/L and 125U/min,respectively. In the range designated,it was increasing in inhibitory effects of ascorbic acid,citric acid,Na HSO3,L-Cysteine and EDTA against enzyme activity with the increasing concentration,and the order as follow：ascorbic acid﹥citric acid﹥L-cysteine﹥EDTA﹥Na HSO3.