摘要
以云南大叶种代表性品种勐库大叶种茶树鲜叶为原料,对以硫酸铵沉淀制备的多酚氧化酶(polyphenol oxidase,PPO)粗酶进行部分酶学性质研究。结果表明,勐库大叶种PPO最适反应p H为4.4,最适反应温度为37℃,对焦性没食子酸、邻苯二酚有催化活性,而对间苯二酚、对苯二酚基本无催化活性。以焦性没食子酸、邻苯二酚为底物时,勐库大叶种PPO的米氏常数(Km)分别为4.2 mmol/L和36.5 mmol/L,最大单位酶活力(Vmax)值分别为2 000 U/m L和5 000 U/m L,且对焦性没食子酸的催化效果优于邻苯二酚。抑制剂乙二胺四乙酸二钠(EDTA-2Na)、亚硫酸钠、抗坏血酸和L-半胱氨酸对勐库大叶种PPO的抑制效果均随抑制剂浓度的增大而增强,其中亚硫酸钠的抑制作用最强。在终浓度为0~10.00 mmol/L范围内,除Na+对勐库大叶种PPO活性有一定的抑制作用外,K^+、Cu^(2+)和Mg^(2+)对勐库大叶种PPO活性均有不同程度的促进作用。不同来源的茶树PPO酶学性质有着明显的区别,可能与品种适制性有直接的联系。
Polyphenol oxidase（PPO, EC 1.10.3.1） has great significance to the growth and development of Camellia sinensis, for instance it participates in adjusting and maintaining the normal physiology and metabolism, plays an essential role in the course of the quality formation of tea products, and contributes to the oxidation reaction of tea polyphenols. The oxidation products, such as quinines, theaflavins and thearubigins, have a remarkable effect on the quality of black tea.The existing researches of C. sinensis PPO involve in various varieties and multiple aspects, including separation and purification, enzymatic property analysis, genetic structure, etc. Nevertheless, there is no research on C. sinensis var.assamica cv. Mengku, even though it carries relative original genetic information and has a great suitability for black tea manufacture.In this study, the fresh leaves of Camellia sinensis var. assamica cv. Mengku were used as materials. The crude polyphenol oxidase（PPO） from tea leaves was extracted by using homogenate extraction technology and purified through（NH4_）_2 SO_4 precipitation. The characteristics including optimum reaction p H, optimum reaction temperature, substratespecificity, Michaelis-Menten constants and the effect of inhibitors and metal ions on its activity were studied. It aims to lay the foundation for regulating PPO activity and illuminating the suitability for black tea manufacture of C. sinensis var.assamica.The results showed that the optimum p H of crude PPO was 4.4, and its optimum temperature was 37 ℃. It had the catalytic activity on catechol and pyrogallic acid, but not on hydroquinone and resorcinol. When pyrogallic acid and catechol as its substrate, their Kmvalues were 4.2 and 36.5 mmol/L, respectively, and their Vmaxvalues were 2 000 and 5 000 U/m L,respectively, indicating that the catalytic efficiency of pyrogallic acid was better. The inhibition of EDTA-2 Na, sodium sulfite, ascorbic acid and L-cysteine on crude PPO was enhanced with the increasing concentratio
出处
《浙江大学学报（农业与生命科学版）》
CAS
CSCD
北大核心
2017年第5期579-588,共10页
Journal of Zhejiang University:Agriculture and Life Sciences
基金
国家自然科学基金(31270731)
关键词
勐库大叶种茶树
多酚氧化酶粗酶
酶学性质
Camelliasinensis var. assamica cv.Mengku
crudepolyphenoloxidase
enzymaticcharacterization
