Abstract: The polyphenol oxidase (PPO) in snow pear flesh was extracted and purified. The results showed that the optimum pH for PPO is 6.4; the optimum temperature for PPO is 25 ℃; the PPO activity changed at different stages; the 1 mol/L sodium sulfite is a better inhibitor and the PPO activity is largest in the interior of pear fleash.Oxidase was purified from snow pear flesh by four steps: Ammonium sulfate fractionation with saturation 30%, ammonium sulfate fractionation with saturation 80%, Sephadex-G200 filtration and HiPrepTM16/10 QXL column chromatography in turn. Through these steps, PPO was purified to electrophoretic homogeneity. SDS-PAGE showed the protein as a single polypeptide with a molecular weight of about 43.0 kD.

Key words: pear, phenol oxidize (PPO), chromatography