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

针对酶法合成茶氨酸中存在的自转肽副反应，合成了L-谷氨酰胺-锌(II)配合物Zn(Gln)2，以其为供体、乙胺为受体、枯草芽孢杆菌B. subtilis GGT为催化剂，酶法制备茶氨酸. 结果表明，Zn(Gln)2在反应主体相稳定性良好，以Zn(Gln)2为供体可有效抑制自转肽副反应；B. subtilis GGT对Zn(Gln)2和Gln的亲和力常数分别为0.53 mmol/L和1.01 mmol/L. 在Zn(Gln)2 6.0 mmol/L、乙胺200 mmol/L及GGT 0.5 U/mL条件下，经37℃反应2 h，茶氨酸浓度最高可达7.38 mmol/L，较以Gln为供体时提高了14.42%.

Investigation on Enzymatic Synthesis of L-Theanine with Zinc(II)-L-Glutamine Complex and Its Mechanism

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.