Development of efficient enzymatic production of theanine by γ-glutamyltranspeptidase from a newly isolated strain of Bacillus subtilis, SK11.004

Background: 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).

Results: 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%.

Conclusion: 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.