The transpeptidase activity of glutaminase from Bacillus amyloliquefaciens (GBA) and Aspergillus oryzae (GAO) to yield γ-[Glu]_n-Phe peptides were verified for the first time. In the presence of Gln and Phe, γ-Glu-Phe and γ-Glu-γ-Glu-Phe were synthesized by GAO, and γ-Glu-Phe, γ-Glu-γ-Glu-Phe, γ-Glu-γ-Glu-γ-Glu-Phe, γ-Glu-γ-Glu-γ-Glu-γ-Glu-Phe, and γ-Glu-γ-Glu-γ-Glu-γ-Glu-γ-Glu-Phe were synthesized by GBA. The K_m values for the transpeptidation catalyzed by GBA and GAO were 47.88 and 153.92 mM (Phe as the acceptor), 84.89 and 236.47 mM (γ-Glu-Phe as the acceptor), indicating that GBA had a greater affinity than GAO for Phe and γ-Glu-Phe in the transpeptidation reaction. The K_m values for the transpeptidation catalyzed by GBA against acceptors, Phe and γ-[Glu]_(1≤n<5)-Phe (47.88–206.47 mM), increased with an elevated number of γ-glutamyl residue within the acceptor. The optimal conditions for γ-[Glu]_n-Phe synthesis were pH 10 and 37 °C for 3 h, 300 mM Gln, 100 mM Phe, 0.05 U/mL GBA. All the γ-[Glu]_(1≤n≤5)-Phe exhibited astringency in water and imparted a kokumi taste to commercial soy sauce and model chicken broth. The astringent threshold values (2.5–3.92 mM) were approximately 3-fold of the kokumi threshold concentrations (0.78–1.53 mM). γ-[Glu]_n-Phe or the post-enzymatic reaction mixture enhanced the umami intensity of commercial soy sauce and model chicken broth.

中文翻译：

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谷氨酰胺和苯丙氨酸存在下，Kokumiγ-[Glu] _n -Phe的合成及感官特性：解淀粉芽孢杆菌或米曲霉催化的谷氨酰胺酶

首次验证了来自解淀粉芽孢杆菌（GBA）和米曲霉（GAO）的谷氨酰胺酶的转肽酶活性，以产生γ-[Glu] _n -Phe肽。在Gln和Phe的存在下，GAO合成了γ-Glu-Phe和γ-Glu-γ-Glu-Phe，γ-Glu-Phe，γ-Glu-γ-Glu-Phe，γ-Glu-γ -Glu-γ-Glu-Phe，γ-Glu-γ-Glu-γ-Glu-γ-Glu-Phe和γ-Glu-γ-Glu-γ-Glu-γ-Glu-γ-Glu-Phe是由GBA合成。GBA和GAO催化的转肽作用的K _m值分别为47.88和153.92 mM（Phe为受体），84.89和236.47 mM（γ-Glu-Phe为受体），表明GBA对GAP的亲和力高于GAO。和γ-Glu-Phe在转肽反应中。该ķ_米用于通过针对GBA受体，Phe和γ-[谷氨酸]催化的转肽值_{（1≤ Ñ <5）} -Phe（47.88-206.47毫摩尔），与受体内升高的数γ谷氨酰残基的增加。γ-[Glu] _n -Phe合成的最佳条件是pH 10和37°C持续3 h，300 mM Gln，100 mM Phe，0.05 U / mL GBA。所有γ-[谷氨酸] _{（1≤ ñ ≤5）} -Phe显示吸水涩味和赋予一个浓厚的口味商业酱油和模型鸡汤。涩味阈值（2.5–3.92 mM）约为kokumi阈值浓度（0.78–1.53 mM）的3倍。γ-[Glu] _n-Phe或酶后反应混合物增强了商业酱油和模型鸡汤的鲜味强度。