Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement & Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences , Xingke Road 723, Tianhe District, Guangzhou 510650, China.
University of Chinese Academy of Sciences , No. 19A Yuquan Road, Beijing 100049, China.
J Agric Food Chem. 2017 Aug 23;65(33):7210-7216. doi: 10.1021/acs.jafc.7b02437. Epub 2017 Aug 10.
Tea (Camellia sinensis) is the most widely consumed beverage aside from water. The flavor of tea is conferred by certain metabolites, especially l-theanine, in C. sinensis. To determine why more l-theanine accumulates in C. sinensis than in other plants, we compare l-theanine contents between C. sinensis and other plant species (Camellia nitidissima, Camellia japonica, Zea mays, Arabidopsis thaliana, and Solanum lycopersicum) and use a stable isotope labeling approach to elucidate its biosynthetic route. We quantify relevant intermediates and metabolites by mass spectrometry. l-Glutamic acid, a precursor of l-theanine, is present in most plants, while ethylamine, another precursor of l-theanine, specifically accumulates in Camellia species, especially C. sinensis. Most plants contain the enzyme/gene catalyzing the conversion of ethylamine and l-glutamic acid to l-theanine. After supplementation with [H]ethylamine, all the plants produce [H]l-theanine, which suggests that ethylamine availability is the reason for the difference in l-theanine accumulation between C. sinensis and other plants.
茶（Camellia sinensis）是除水之外最广泛饮用的饮料。茶的味道是由某些代谢物赋予的，尤其是 C. sinensis 中的 l-茶氨酸。为了确定为什么 C. sinensis 中积累的 l-茶氨酸比其他植物多，我们比较了 C. sinensis 与其他植物物种（Camellia nitidissima、Camellia japonica、Zea mays、Arabidopsis thaliana 和 Solanum lycopersicum）之间的 l-茶氨酸含量，并使用稳定同位素标记方法阐明其生物合成途径。我们通过质谱定量分析相关的中间产物和代谢物。l-谷氨酸，l-茶氨酸的前体，存在于大多数植物中，而另一种 l-茶氨酸的前体，乙胺，特别在茶科植物中积累，尤其是 C. sinensis。大多数植物都含有催化乙胺和 l-谷氨酸转化为 l-茶氨酸的酶/基因。在补充[H]乙胺后，所有植物都产生[H]l-茶氨酸，这表明乙胺的可用性是 C. sinensis 和其他植物中 l-茶氨酸积累差异的原因。
