酶促合成茶黄素的茶鲜叶酶源筛选

Screening of the Sources of Enzymes from Fresh Tea Leaves for the Enzymatic Synthesis of Theaflavins

通过对不同季节、不同采摘标准的20个茶树品种鲜叶的多酚氧化酶(PPO)活性及其同工酶分析,筛选出了3种PPO活性较高的茶鲜叶原料,然后以其匀浆液以及在匀浆液中添加速溶绿茶的方法,以催化速溶绿茶酶促合成茶黄素的效率为标准筛选了酶促合成茶黄素的茶鲜叶酶源。结果表明,各茶树品种茶鲜叶PPO活性以夏季一芽二叶较高,酶活性较高的3个品种依次为政和大白茶、福云6号及桃源大叶;不同品种茶鲜叶的PPO同工酶在谱带数目、迁移率和谱带染色深浅3个方面有差异,20个品种有2条相同的同工酶带,其Rf值分别为0.27和0.53,政和大白茶、桃源大叶、福云6号均有5条明显的同工酶带,且以政和大白茶的谱带染色最深;单位质量的政和大白茶鲜叶匀浆液自身酶促合成茶黄素的量高于桃源大叶与福云六号;参加酶促反应合成茶黄素的儿茶素主要为EC、EGCG和ECG;添加速溶绿茶作为底物合成茶黄素的量远高于茶鲜叶自身酶促合成茶黄素的量,其中政和大白茶反应体系中茶黄素的质量浓度达212.01mg/L,为自身酶促合成茶黄素质量浓度(39.05mg/L)的5.43倍。

Fresh tea leaves of twenty cultivars of tea plants were investigated. The season of harvesting and the methods of plucking were concerned as factors which could affect the enzymic activity of the endogenous polyphenol oxidase（PPO） as well as its isozyme. As a result, three of the tea cultivars were distinctively selected out. In the order of the enzymic activity from high to low, they were Zheng-he White Tea, Fu-yun 6th and Large-leaved Tao-yuan Tea. The fresh tea leaves were mashed, the effectivenesss of enzymic synthesis of theaflavins were observed, meanwhile, instant green tea was considered as an added substrate to promote the yield. The results showed that the one bud and two leaves shoot exhibited high enzymic activity of PPO, the different tea cultivars presented the isozymes of PPO with diversities in three aspects including the number of the isozymes bands, value of retention factor and the darkness of spectral color. Two isozyme bands of PPO appeared in every one of the sampled twenty tea cultivars, with the Rf value of 0.27 and 0.53, each of Zheng-he White Tea, Fu-yun 6th and Large-leaved Tao-yuan Tea possessed five evident isozyme bands, Zheng-he White Tea exhibited the darkest of the spectral color, while it yielded highest theaflavins per unit mashed tea leaves than those of Fu-yun 6th and Large-leaved Tao-yuan Tea produced, EC, EGCG and ECG were the major polyphenols which were involved in the enzymic synthesis; the yield of theaflavins was enormously enhanced by the added substrate of instant green tea, the theaflavins concentration of 212.01 mg/L was gained from the Zheng-he White Tea processing system, which reached the 5.43 times of the yield producing by the fresh tea leaves without the addition of instant green tea substrate.