Identification and characterization of N9-methyltransferase involved in converting caffeine into non-stimulatory theacrine in tea
Identification and characterization of N9-methyltransferase involved in converting caffeine into non-stimulatory theacrine in tea
复制标题
茶中咖啡因转化为非刺激性茶碱的 N9-甲基转移酶的鉴定和表征
DOI：
10.1038/s41467-020-15324-7
复制
发表时间：
2020-03-19
影响因子：
16.6
通讯作者：
He, Rong-Rong
中科院分区：
文献类型：
--
作者：
Zhang, Yue-Hong;Li, Yi-Fang;He, Rong-Rong
咖啡因是黄嘌呤生物碱的主要成分，通常在许多受欢迎的饮料中消费。由于咖啡因偶尔会产生副作用，以自然的方式减少咖啡因的摄入具有重要的意义和经济意义。最近的研究表明，在稀有茶树茶树中，咖啡因可以转化为非刺激性茶碱。Kucha(Kucha)，它涉及咖啡因C8的氧化和N9位的甲基化。然而，其潜在的分子机制仍不清楚。在这里，我们从Kucha中鉴定了茶碱合成酶CkTcS，它具有新的N9-甲基转移酶活性，以1，3，7-三甲基尿酸为底物，而不是咖啡因，证实C8氧化发生在N9-甲基化之前。CkTcS复合体的晶体结构揭示了N9-甲基化所需的关键残基，为茶树中咖啡因N-甲基转移酶如何通过微调其活性位点来催化区域选择性N-甲基化提供了深入的见解。这些结果可能对未来无咖啡因饮料的发展起到指导作用。
Caffeine is a major component of xanthine alkaloids and commonly consumed in many popular beverages. Due to its occasional side effects, reduction of caffeine in a natural way is of great importance and economic significance. Recent studies reveal that caffeine can be converted into non-stimulatory theacrine in the rare tea plant Camellia assamica var. kucha (Kucha), which involves oxidation at the C8 and methylation at the N9 positions of caffeine. However, the underlying molecular mechanism remains unclear. Here, we identify the theacrine synthase CkTcS from Kucha, which possesses novel N9-methyltransferase activity using 1,3,7-trimethyluric acid but not caffeine as a substrate, confirming that C8 oxidation takes place prior to N9-methylation. The crystal structure of the CkTcS complex reveals the key residues that are required for the N9-methylation, providing insights into how caffeine N-methyltransferases in tea plants have evolved to catalyze regioselective N-methylation through fine tuning of their active sites. These results may guide the future development of decaffeinated drinks.