State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China.
J Sci Food Agric. 2010 Dec;90(15):2563-7. doi: 10.1002/jsfa.4120.
Theanine, a unique amino acid found almost exclusively in tea plants, has various favourable physiological and pharmacological functions in humans. Gamma-glutamyltranspeptidase (GGT, EC 2.3.2.2) is considered to be the most effective enzyme for the production of theanine. In fact, GGT can catalyse the transfer of γ-glutamyl moieties from γ-glutamyl compounds to water (hydrolysis) or to amino acids and peptides (transpeptidation).
A novel strain, SK11.004, which produces GGT with high theanine-forming ability was isolated from fermented shrimp paste and identified as Bacillus subtilis through its physiological and biochemical properties as well as its 16S rDNA sequence analysis. Theanine (18.9 mmol L(-1)) was synthesised by GGT (0.06 U mL(-1)) through transfer reaction in the presence of glutamine (20 mmol L(-1)) as a donor and ethylamine HCl (50 mmol L(-1)) as an acceptor at pH 10 and 37 °C for 4 h, the conversion rate being up to 94%.
The enzymatic synthesis of theanine using GGT from a newly isolated strain Bacillus subtilis SK11.004 was found to be an efficient method. Moreover, compared with others, the GGT from B. subtilis SK11.004 exhibited the highest ratio of transferring activity to hydrolytic activity using glutamine, suggesting a high potential application in the production of theanine and other functional γ-glutamyl compounds.
茶氨酸是一种独特的氨基酸，几乎只存在于茶树中，对人体具有多种有益的生理和药理功能。γ-谷氨酰转肽酶（GGT，EC 2.3.2.2）被认为是生产茶氨酸最有效的酶。事实上，GGT 可以催化 γ-谷氨酰基从 γ-谷氨酰化合物转移到水（水解）或氨基酸和肽（转肽）。
从发酵虾酱中分离到一株产 GGT 能力高的新型菌株 SK11.004，通过生理生化特性和 16S rDNA 序列分析鉴定为枯草芽孢杆菌。在 pH 10 和 37°C 下，GGT（0.06 U mL(-1)) 通过转移反应在谷氨酰胺（20 mmol L(-1))作为供体和乙胺盐酸盐（50 mmol L(-1))作为受体的存在下合成茶氨酸（18.9 mmol L(-1))，转化率高达 94%。
用新分离的枯草芽孢杆菌 SK11.004 的 GGT 进行茶氨酸的酶法合成是一种有效的方法。此外，与其他菌株相比，枯草芽孢杆菌 SK11.004 的 GGT 对谷氨酰胺的转移活性与水解活性之比最高，表明其在茶氨酸和其他功能性 γ-谷氨酰化合物生产方面具有很高的应用潜力。
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