河南农业大学学报

以菜花为原料制备粗酶液,以邻苯二酚为底物,采用分光光度法在420 nm波长下研究温度、pH值、底物浓度对菜花多酚氧化酶活性的影响,建立相应的酶促褐变反应动力学方程,并探讨了氯化镁、十二烷基硫酸钠、亚硫酸氢钠、L-半胱氨酸、抗坏血酸等对酶活性的影响.结果表明,菜花多酚氧化酶的最适pH值为7.0,最适温度为50℃,50℃加热10 min仍保留61%的活性.其米氏常数和最大反应速率分别是0.056 23 mol·L-1和8.650 5U·min-1.氯化镁、十二烷基硫酸钠可增强菜花PPO活性,亚硫酸氢钠、L-半胱氨酸、抗坏血酸可抑制其活性.

The properties of polyphenol oxidase extracted from cauliflower were investigated.The cauliflower polyphenol oxidase activities were spectrophotometrically determined at 420 nm with catechol as substrate under conditions of different temperature,pH value and substrate concentration.The reaction kinetic equation was also established in this research.The results showed that the optimal pH value and temperature of cauliflower PPO was 7.0 and 50 ℃,respectively.61% of the activity of cauliflower PPO was maintained after being heated at 50 ℃ for 10 min.The Michaelis constant and maximum velocity of PPO was 0.056 23 mol·L-1 and 8.650 5 U·min-1,respectively.The PPO activity was enhanced by magnesium chloride and sodium dodecyl sulfate-polyacrylamide,and could be inhibited by sodium bisulfite as well as L-cysteine and ascorbic acid.