【摘要】 通过丙酮酚法从百合中提取出多酚氧化酶(PPO)的粗酶液。以儿茶酚为底物时它有两个最适pH,分别为4.0、7.0,在pH5.0-6.5之间酶活力可以在4℃保持至少10h。PPO的最适温度为40℃,从40℃开始酶出现热失活,热失活速度符合一级反应动力学。PPO除对L-酪氨酸没有活力外,对儿茶酚、儿茶素、没食子酸均有活力,其中对儿茶素具有最好的底物特异性。亚硫酸钠对PPO的抑制作用最强,高浓度的抗坏血酸、半胱氨酸、硫脲也有很好的抑制作用,氯化钠、氯化钙、柠檬酸的抑制作用较差。更多还原

【Abstract】 Crude polyphenol oxidase (PRO) was extracted from lily by the preparation of acetone powder. The enzyme activity showed two pH optima, at pH 4.0 and 7.0 with catechol as substrate, and it was stable in the pH range from 5.0 to 6.5 at 4℃ for 10h. The optimum temperature was 40℃, and the enzyme began to inactivate at 40℃. Heat inactivation of PRO followed first order kinetics. Lily PRO had activity toward catechol , catechin, and gallic acid, and activity toward L-tyrosine was not observed. The most effective inhibitor was sodium sulpfite, however, ascorbic acid, L-cysteine, and thiourea were also effective inhibitors at high concentration. But NaCI, CaCI2, and citric acid were poor inhibitors of the enzyme.更多还原