荔枝果肉多酚氧化酶酶学性质研究

目的]为研究荔枝果肉多酚氧化酶（PPO）的作用机制,控制荔枝果肉在贮藏和加工过程中的酶促褐变提供理论依据。方法]从荔枝果肉中提取多酚氧化酶,并对其酶学性质进行研究。结果]荔枝果肉PPO的最适反应温度为55℃,对热稳定性较强,90℃水浴保温30 min后剩余相对酶活为22.6%;pH值为7.0时该酶的活力最强,在pH值6.5~8.0范围内酶活力较稳定;邻苯二酚与该酶的结合能力最强,其次为4-甲基儿茶酚;谷胱甘肽为该酶的最好抑制剂,其次为半胱氨酸、抗坏血酸、NaF和亚硫酸钠;SnCl2和FeSO4对该酶活性有抑制作用,而CuSO4、MgC l2和CaCl2对其活性有促进作用。结论]该研究确定了荔枝果肉多酚氧化酶的最适作用条件。

Study on Enzymatic Characteristics of Polyphenol Oxidase (PPO) in Litchi Pulp

Objective]The aim was to provide the theoretical basis for studying the action mechanism of polyphenol oxidase(PPO) in litchi pulp and controlling the enzymatic browning of litchi pulp during storage and processing.Method]Polyphenol oxidase was extracted from litchi pulp and its enzymatic characteristics were studied.Result]The optimum temperature of PPO in litchi pulp was 55 ℃ and its thermostability was good.After 30 min of water bathing at 90 ℃,the remaining relative enzyme activity was 22.6%.The enzyme activity was the strongest when pH value was 7.0.And the enzyme activity was stable when pH value was 6.5-8.0.The binding ability of catechol with the enzyme was the strongest,followed by 4-methyl catechol.Glutathione was the best inhibitor of the enzyme,followed by cysteine,ascorbic acid,NaF and sodium sulfite.SnCl2 and FeSO4 could inhibit the enzyme activity.But CuSO4,MgCl2 and CaCl2 could increase the enzyme activity.Conclusion]This study identified the optimum conditions of polyphenol oxidase in litchi pulp.