Abstract:

Polyphenoloxidase (PPO) was prepared from fruit powder of Xinli No.7 by salt-out precipitation with saturated ammonium sulphate solution followed by purification by DEAE-Sephadex A-50 column chromatography and its enzymological properties were investigated. The optimum working temperature and pH value of Xinli No.7 PPO were 25 ℃ and 6.5 separately. The enzyme was inactivated by both heating treatment for 135 s at 99 ℃ and microwave treatment for 15 s at 100 Hz. The affinity towards various substrates declined in the following order of caffeic acid ＞ chlorogenic acid ＞ catechol. No obvious inhibition effects of 0.5%－3.0% NaCl, 0.01%－0.1% citric acid and 0.05%－0.3% EDTA-2Na were observed on the PPO activity while VC, L-Cys, NaHSO3 and Na2S2O3 at the concentration of 0.01%－0.1% all exhibited marked inhibition effects and VC was the most effective inhibitor.

Key words: Xinli No.7, polyphenoloxidase, purification, characteristics