麦麸中多酚氧化酶的分离纯化及其性质的初步研究

PARTIAL PURIFICATION AND PRELIMINARY CHARACTERIZATION OF WHEAT BRAN POLYPHENOLOXIDASE

通过硫酸铵分级沉淀、DEAE-纤维素层析和Sephadex G200层析等方法,从小麦麸皮中分离并纯化了多酚氧化酶。该酶在60℃保温1h仍有44%的活性,最适反应pH为5.6。该酶可作用于多巴胺、多巴及邻苯二酚,但对绿原酸和酪氨酸没有作用。在以多巴胺为底物时,该酶的K_m为5.0 mmol/L。低浓度的亚硫酸氢钠、L-抗坏血酸和苯基硫脲对该酶均有抑活作用。

Polyphenoloxidase(PPO) in the wheat bran was extracted and partially purifiedby 60%(NH_4)_2SO_4 precipitation and chromatography. The optimum reaction pHfor PPO was 5.6. The Michalis constant (K_m) of this enzyme was 5.0 mmol/L atpH5.6. Wheat bran PPO can interact with dopamine, DOPA and orthodiphenol,neither the chlorogenic acid nor tyrosine was attacked. 44% of PPO activity re-mained after incubation at 60℃ for one hour. Among inhibitors of PPPO weresodium sulfite (0.05 mmol/L), L-ascobic acid (0.25 mmol/L) and phenylthiourea(0.005 mmol/L).