Properties and inhibitions of polyphenoloxidase and peroxidase from Asparagusplettuce

The activities of polyphenoloxidase( PPO) and peroxidase( POD) from Asparagusplettuce were determined by spectrophotometer. Enzyme stabilities,the effects of temperature,p H,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 p H of PPO and POD were 50℃ and 40℃,p H6.0 and p H6.5,respectively. Activities of PPO and POD decreased with increasing temperature. Kinetic equation for PPO and POD were V = 342.566S/( 5.9 × 10- 3+ S) and V =3403.008S/( 6.88 × 10- 4+S),respectively.Inhibition effects were as follows: VC> L- Cys > Na HSO3> citric acid> EDTA > benzoicacid > succinic acid for PPO,EDTA > VC> L- Cys > citric acid > Na HSO3> succinic acid >benzoic acid for POD. Orthogonal experiments showed that the optimum inhibition conditions were as follows:Na HSO39 mmol / L,L- Cys 5mmol / L and VC5 mmol / L for PPO,VC0.2mmol / L,EDTA 0.2mmol / L and L- Cys1.4mmol / L for POD,respectively.