Theanine synthetase

Biosynthesis of theanine occurs in the root of the tea plant with the aid of the enzyme theanine synthetase (also called L-glutamate ethylamine ligase or L-glutamate ethyl-amine ligase, EC 6.3.1.6) (figure 16.3). 

Since L-theanine synthetase is quite labile, its further purification may be hampered. There is no report on the purification and property on this enzyme. The biosynthesis of theanine from L-glutamate and ethylamine is shown in the following equation of the L-theanine synthetase catalytic reaction ... 

The biosynthesis of theanine from glutamate and ethylamine is catalyzed by theanine synthetase (L-glutamate ethylamine ligase, EC 6.3.1.6), which is an ATP-dependent enzyme and quite unstable. All attempts to biosynthesize theanine using this enzyme should overcome the problems of the ATP generating system. 

Tachiki et al. reported the production of theanine from glutamate and ethyl-amine through the coupling of baker s yeast preparations and bacterial glutamine synthetase. Because of the low reactivity of glutamine synthetase with ethylamine and the difficulty in pH control of the reaction mixture, the yield was not satisfatory. The production of theanine with cultured cells of Camellia sinensis has been performed, but it took a 4-week cultivation period. 

Yamamoto, S., M. Wakayama, and T. Tachiki. 2005. Theanine production by coupled fermentation with energy transfer employing Pseudomonas taetrolens Y-30 glutamine synthetase and baker s yeast cells. Biosci. Biotechnol. Biochem. 69 784-789. 

Theanine is formed by the direct combination of ethylamine and glutamate in the presence of ATP. The enzyme is separate from normal glutamine synthetase as ammonia has no effect on the reaction (Sasaokaet al 1%5). Alanine is the most direct precursor of ethylamine theanine is then incorporated into the phloroglucinol nucleus of catechins (Takeo, 1974). 

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