Guangdong Provincial Key Laboratory of Applied Botany, & Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement, South China Botanical Garden, Chinese Academy of Sciences, Xingke Road 723, Tianhe District, Guangzhou 510650, China.
Guangdong Provincial Key Laboratory of Applied Botany, & Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement, 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.
Food Res Int. 2017 Jun;96:206-214. doi: 10.1016/j.foodres.2017.03.049. Epub 2017 Apr 5.
Tea (Camellia sinensis) aroma is an important factor affecting tea quality. Many tea aroma compounds are present as glycosidically conjugated forms in tea leaves, and can be hydrolyzed by β-glucosidase (β-Glu) and β-primeverosidase to release free tea aromas. β-Primeverosidase has been identified and functionally characterized, while β-Glu has not been identified in tea leaves. In the present study, we established a yeast expression system to recombine CsGH1BG1, CsGH3BG1, and CsGH5BG1, which belonged to GH1, GH3, and GH5 families in plants, respectively. These three recombinant Csβ-Glus hydrolyzed the β-glucopyranosidically conjugated aromas to form free aromas, suggesting that there was no specific Csβ-Glus for the hydrolysis of β-glucopyranosidically conjugated aromas in vitro. Furthermore, subcellular localization of the Csβ-Glus indicated that CsGH1BG1 and CsGH3BG1 were located in the cytosol and vacuole, respectively, while CsGH5BG1 was located in the cell wall. This suggested that CsGH1BG1 and CsGH3BG1 might be responsible for the hydrolysis of β-glucopyranosidically conjugated aromas in tea leaves during the tea manufacturing process. This study provides the first evidence of Csβ-Glus in tea leaves, and will advance understanding of tea aroma formation.
茶（Camellia sinensis）香气是影响茶叶品质的重要因素。许多茶香气化合物以糖苷结合的形式存在于茶叶中，可以被β-葡萄糖苷酶（β-Glu）和β-樱草糖苷酶（β-primeverosidase）水解，释放出游离的茶香。β-樱草糖苷酶已被鉴定并具有功能特征，而β-Glu 尚未在茶叶中被鉴定。在本研究中，我们建立了一个酵母表达系统来重组属于植物 GH1、GH3 和 GH5 家族的 CsGH1BG1、CsGH3BG1 和 CsGH5BG1。这三种重组的 Csβ-Glus 水解β-葡萄糖苷结合的香气，形成游离的香气，表明体外没有专门的 Csβ-Glus 来水解β-葡萄糖苷结合的香气。此外，Csβ-Glus 的亚细胞定位表明 CsGH1BG1 和 CsGH3BG1 分别位于细胞质和液泡中，而 CsGH5BG1 位于细胞壁中。这表明 CsGH1BG1 和 CsGH3BG1 可能负责在茶叶加工过程中水解β-葡萄糖苷结合的香气。本研究首次在茶叶中鉴定出 Csβ-Glus，将有助于深入了解茶香的形成。
