Investigation on Enzymatic Synthesis of L-Theanine with Zinc(Ⅱ)-L-Glutamine Complex and Its Mechanism
以L-谷氨酰胺—锌(Ⅱ)配合物为供体酶法制备茶氨酸及其反应机理

To restrain the side reaction of autotranspeptidation, the complex of L-glutamine-Zn(Ⅱ) Zn(Gln)2] was prepared and used for enzymatic synthesis of theanine via γ-glutamyltranspeptidation (GGT) reaction. The stability and reactivity of Zn(Gln)2 were satisfactory under the reaction conditions. Moreover, autotranspeptidation was restrained effectively when Zn(Gln)2 instead of L-glutamine (Gln) was used as the γ-glutamyl donor. The kinetic parameter Km of B. subtillus GGT toward Zn(Gln)2 and Gln was calculated to be 0.53 and 1.01 mmol/L respectively. Under the conditions of 6 mmol/L Zn(Gln)2, 200 mmol/L ethylamine, and 0.5 U/mL GGT, 7.38 mmol/L of theanine was obtained after incubation at 37℃ for 2 h, indicating an increase of 14.42% compared with that using Gln as the donor substrate.