STUDY ON THE CHARACTERS OF POLYPHENOLOXIDASE AND INHIBITOR IN DUCK-BILLED PEAR

The activity of duck-billed pear polyphenol oxidase(PPO)was spectrophotometer at 420 nm using catechol as substrate.The effects of the different substrate,temperature,pH,substrate concentration and inhibitors on PPO were studied and the reaction kinetic equation was established.The results showed that the optimum substrate,temperature and pH were catechol,30 ℃ and pH 6.6,respectively.The reaction kinetic of enzymatic browning in this experiment built accorded with Michaelis equation modle.The Km,Vmax and kinetic Equation were 0.333 mol/L,0.089 U/min and v=0.089[S]/(0.333+[S])using catechol as substrate,respectively.The four inhibitors had different effects on inhibiting enzymatic browning and the inhibiting effects as follow:ascorbic acidEDTACitric acidsodium bisulphite