γ-Glutamyltransferase (GGT) can catalyze the transfer of a γ-glutamyl group to amino acids or peptides. Bacterial GGTs have a wide substrate specificity, which means that a variety of γ-glutamyl amino acid derivatives or peptides can be synthesized under GGT catalysis. In this work, in order to enhance the expression and stability of GGT, a recombinant plasmid harboring Bacillus amyloliquefaciensggt gene with a Usp45 signal peptide gene fused upstream was constructed and transferred into Lactococcus lactis NZ9000 to express BaGGT. After on-column hydrolysis and purification by immobilized metal affinity chromatography, 90.2 ± 0.7 mg/L of BaGGT-6His with an enzymatic activity of 57.3 ± 0.9 U/mg was purified. Subsequently, BaGGT-6His was immobilized onto magnetic mesoporous nanoparticles (Fe₃O₄NPs) by covalent binding. The immobilized BaGGT-6His largely retained the activity and, importantly, could be recovered and reused. After optimization of the production and immobilization conditions, the biotechnologically relevant product l-theanine was synthesized with free and immobilized BaGGT-6His.

中文翻译：

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表达解淀粉芽孢杆菌γ谷氨酰转移在乳酸乳球菌和固定化的磁性纳米粒子

γ-谷氨酰转移酶 (GGT) 可以催化 γ-谷氨酰基团向氨基酸或肽的转移。细菌 GGT 具有广泛的底物特异性，这意味着在 GGT 催化下可以合成多种 γ-谷氨酰氨基酸衍生物或肽。在这项工作中，为了增强 GGT 的表达和稳定性，构建了一个含有解淀粉芽孢杆菌ggt基因的重组质粒，并在上游融合了 Usp45 信号肽基因，并将其转移到乳酸乳球菌中。NZ9000 到快递 BaGGT。经柱上水解和固定化金属亲和层析纯化后，纯化得到 90.2 ± 0.7 mg/L 酶活性为 57.3 ± 0.9 U/mg 的 BaGGT-6His。随后，通过共价结合将 BaGGT-6His 固定在磁性介孔纳米粒子 (Fe ₃ O ₄ NPs) 上。固定化的 BaGGT-6Hi 在很大程度上保留了活性，重要的是，可以回收和再利用。在优化生产和固定化条件后，生物技术相关产品l-茶氨酸与游离和固定化的 BaGGT-6His 合成。