毛酸浆多酚氧化酶的酶学特性研究

以毛酸浆中多酚氧化酶（PPO）为研究对象，采用分光光度法在420 nm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2 min，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=0.025 mol/L，Vmax=125 U/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 420 nm. 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 2 min. The kinetics of enzyme-catalyzed reaction of PPO was in accord with Michaelis-Menten equation, with Km and Vmax values of 0.025 mol/L and 125 U/min, respectively. In the range designated, it was increasing in inhibitory effects of ascorbic acid, citric acid, NaHSO3, L-Cysteine and EDTA against enzyme activity with the increasing concentration , and the order as follow：ascorbic acid﹥citric acid﹥L-cysteine﹥EDTA﹥NaHSO3