摘要
采用分光光度法测定莴笋多酚氧化酶(PPO)活性,考察底物特异性、pH值、温度、热稳定性、底物浓度、金属离子及抑制剂对PPO酶活特性的影响,研究莴笋PPO酶学特性。结果表明,莴笋PPO的最适底物为邻苯二酚,最适pH值5.0,最适温度25℃;90℃热处理60 s莴笋PPO酶活基本完全丧失;莴笋PPO最适底物浓度为0.10 mol/L,PPO酶促褐变反应动力学符合米氏方程,相应的动力学参数Km=0.667 mol/L,Vmax=826.4 OD/min;Mg2+、Ca2+、Mn2+、Zn2+对PPO酶活有一定的的抑制作用,Cu2+和Fe3+对PPO酶活有一定的促进作用;五种抑制剂对抑制莴笋PPO酶活力均具有一定的作用,且抑制作用随抑制剂浓度的增大而加强,试验范围内抑制作用由强到弱依次为:抗坏血酸>L-半胱氨酸>Na HSO3>柠檬酸>EDTA,抗坏血酸对莴笋PPO酶活的抑制效果最佳。
The enzyme activity of polyphenol oxidase（PPO） from lettuce was detected by spectrophotometry. The effects of substrate specificity, pH value, temperature, thermal stability, substrate concentration, metal ions and inhibitors on the enzyme activity were studied. The results indicated that the optimum substrate, pH value, and temperature for the PPO were catechol, pH 5.0 and 25 ℃, respectively. The complete enzyme activity of lettuce PPO was almost lost after heating at 90 ℃ for 60 s. The optimal substrate concentration was 0.10 mol/L, and the kinetics of the PPO browning reaction complied with the law of Michaelis-Menten equation with Kmand Vmaxvalues of0.667 mol/L and 826.4 OD/min, respectively. Mg2＋, Ca2＋, Mn2＋and Zn2＋had a certain inhibitory effect on the enzyme, while the enzyme activity could be activated by Cu2＋and Fe3＋. Five kinds of inhibitors at 0.10 mol/L concentration had inhibitory effect on the enzyme activity, and the inhibitory effect increased with the increasing concentrations. The inhibition effect order of the inhibitors was as follows： ascorbic acid 〉L-cysteine 〉NaHSO3〉citric acid〉EDTA, ascorbic acid showed the most significant inhibition effect on the PPO.
出处
《保鲜与加工》
CAS
北大核心
2018年第1期71-75,共5页
Storage and Process
基金
陕西省科技厅资助科研项目(2014JQ2055)
陕西省教育厅资助科研项目(2014JK1145)
关键词
莴笋
多酚氧化酶
酶学特性
lettuce
polyphenol oxidase（PPO）
enzymatic properties
