莴笋多酚氧化酶、过氧化物酶的特性及抑制作用研究

Properties and inhibitions of polyphenoloxidase and peroxidase from Asparagusplettuce

采用分光光度法测定莴笋多酚氧化酶(PPO)和过氧化物酶(POD)的活性,研究酶的稳定性、温度、p H、底物浓度及几种抑制剂对其活性的影响,建立相应酶促动力学方程,利用正交实验探讨最佳抑制条件。结果表明,PPO和POD最适温度分别为50℃和40℃,最适p H分别为6.0和6.5,随温度不断升高,PPO和POD活性逐渐下降。动力学方程分别为V=342.566[S]/(5.9×10-3+[S])和V=3403.008[S]/(6.88×10-4+[S])。对PPO抑制强弱为:VC>L-Cys>Na HSO3>柠檬酸>EDTA>苯甲酸>琥珀酸,对POD抑制强弱为:EDTA>VC>L-Cys>柠檬酸>Na HSO3>琥珀酸>苯甲酸。正交实验表明,对PPO最佳抑制条件为:Na HSO39mmol/L、L-Cys 5mmol/L及VC5mmol/L。对POD最佳抑制条件为:VC0.2mmol/L、EDTA 0.2mmol/L及L-Cys 1.4mmol/L。

The activities of polyphenoloxidase （ PPO ） and peroxidase （POD） from Asparagusplettuce were determined by spectrophotometer. Enzyme stabilities, the effects of temperature, pH, substrate concentration and several inhibitors on PPO and POD, and their corresponding reaction kinetics equation were studied.Orthogonal experiments were used to optimize inhibition technology.The results showed that the optimum temperature and pH of PPO and POD were 50℃ and 40℃, pH6.0 and pH6.5, respectively.Activities of PPO and POD decreased with increasing temperature. Kinetic equation for PPO and POD were V = 342.566 [ S ]/（5.9 × 10^-3 ＋ [ S ] ） and V = 3403.008[ S]/（6.88 × 10^-4 ＋ [ S] ） ,respectively.Inhibition effects were as follows：Vc 〉 L-Cys 〉 NaHSO3 〉 citric acid 〉 EDTA 〉 benzoicacid 〉 succinic acid for PPO, EDTA 〉 Vc 〉 L- Cys 〉 citric acid 〉 NaHSQ 〉 succinic acid 〉 benzoic acid for POD. Orthogonal experiments showed that the optimum inhibition conditions were as follows： NaHSO39mmol/L, L-Cys 5mmol/L and Vc 5mmol/L for PPO, Vc 0.2mmol/L, EDTA 0.2mmol/L and L-Cys ].4mmol/L for POD,respectively.