八角莲多酚氧化酶的酶学性质

Enzymatic Properties of Polyphenol Oxidase from Dysosma versipellis(Hance.) M.Cheng

以邻苯二酚为底物,研究八角莲多酚氧化酶(polyphenol oxidase,PPO)粗提液的酶学特性。结果表明,底物邻苯二酚最适浓度为1.0 mol/L,八角莲PPO的最适p H值为7.0,最适温度为30℃,90℃高温处理10 min,八角莲PPO酶活力仅剩11.92%。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和vmax分别为0.230 7 mol/L和769.23 U/min。抗坏血酸、甘氨酸、乙二胺四乙酸、柠檬酸对酶活性具有抑制作用,十二烷基硫酸钠表现出激活作用,亚硫酸氢钠对酶活性的抑制作用强于硫代硫酸钠,Al3+和Cu2+对酶活性具有一定的激活作用,Ca2+对酶活性有一定的抑制作用,Mg2+、Fe2+和Fe3+对酶活性影响不显著。

Enzymatic characterization of polyphenol oxidase（PPO） from the leaves of Dysosma versipellis（Hance.） M.Cheng was investigated using catechol as the reaction substrate.The results showed that the optimal substrate was catechol at a concentration of 1.0 mol/L,and the optimal p H and temperature for this enzyme were 7.0 and 30 ℃,respectively.The remaining activity of PPO was 11.92% after thermal treatment at 90 ℃ for 10 min.The kinetics of PPO reaction was fit to the Michaelis-Menten equation,with Km and vmax value of 0.230 7 mol/L and 769.23 U/min,respectively.Different inhibitory effects on PPO among ascorbic acid,glycine,EDTA and citric acid were observed.Na HSO3 showed stronger inhibitory effect on PPO than Na2S2O3.The PPO could be activated by Al3＋,Cu2＋ and SDS.Ca2＋ had certain inhibitory effect on the PPO enzyme.In contrast,Mg2＋,Fe2＋ and Fe3＋ had no significant effect on the enzyme activity（P 0.05）.