甘蔗多酚氧化酶酶学特性及应用研究

对甘蔗多酚氧化酶(PPO)进行提取和部分纯化,研究了PPO的酶学特性.结果表明:以邻苯二酚为底物,甘蔗PPO酶促反应米氏常数Km为54.4 mmol/L,米氏方程:V=1250[S]/(54.4+[S]).蔗汁中邻位多酚类物质是甘蔗PPO的最适反应底物.最适反应条件为:pH值6.2,40℃;该酶在pH5.8和温度低于3℃0时较稳定.试验了6种甘蔗PPO抑制剂:单独使用柠檬酸、草酸、乙二胺四乙酸(EDTA)对PPO活力抑制效果不明显;70 mg/L亚硫酸氢钠、110 mg/L抗坏血酸、120 mg/L硫代硫酸钠可完全抑制PPO活力.现行甘蔗提汁的浸渗工艺较适合蔗汁酶促褐变反应,应作相应的调整.

Enzymatic characterization and application of a polyphenol oxidase from sugarcane

Experiments were performed to extract and purify the polyphenoloxidase (PPO) in sugar-cane. The characteristics Of PPO were also studied. The result showed that using catechol as the substrate, the kinetic equation of PPO was V = 1250[S]/ (54. 4 + [S]) and Km was 54. 4 mmol/L. The O-polyphenols in sugarcane was the optimum substrates. The optimum pH value and tempera-ture were 6. 2 and 40℃respectively. Enzyme was relatively stable at pH5.8 and temperature below 30℃. Six kinds of sugarcane PPO inhabitants were tested. The inhibited effects of citric acid, oxalic acid, ethylenediaminetetraacetic acid(EDTA) on PPO were not obvious. 70 mg/L sodium bisulfite, 110 mg/L ascorbic acid, 120 mg/L sodium thiosulfate could inhibit PPO activity completely. The imbibition technology of the current extraction process was suitable for juice enzymatic browning re-action, so it should be adjusted accordingly.