Effects of pH and dissolved oxygen on the synthesis of γ‐glutamyltranspeptidase from Bacillus subtilis SK 11.004

BACKGROUND: γ‐Glutamyltranspeptidase (GGT; EC 2.3.2.2) is a widely distributed enzyme that is of interest in the food industry. In this study the effects of pH and dissolved oxygen (DO) on GGT synthesis from Bacillus subtilis SK 11.004 were investigated. RESULTS: GGT production increased to 0.5 U mL^?1 when the pH value was controlled at 6.5. The control of a single DO level revealed that the highest specific growth rate (3.42 h^?1) and GGT production rate (0.40 U g^?1 mL^?1) were obtained at DO levels of 40 and 10% respectively. To satisfy the different oxygen demands at different stages of cell growth and GGT synthesis, a stage DO level control strategy was designed as follows: 40% from 0 to 4 h, 30% from 4 to 6 h and 10% from 6 to 18 h. Furthermore, the maximum biomass (2.27 g L^?1) and GGT production (3.05 U mL^?1) could be obtained using a fermentation strategy combining a constant pH value with stage DO level control. CONCLUSION: The proposed fermentation strategy resulted in a 13.7‐fold increase in GGT production. This finding should be of great importance for the industrial production of GGT. Copyright © 2011 Society of Chemical Industry     

谷氨酰转肽酶细胞合成L-谷氨酰正丙胺的研究

摘要：利用谷氨酰转肽酶细胞合成L-谷氨酰正丙胺,采用L-谷氨酰肼和正丙胺作为底物,考察底物浓度、温度、pH、催化剂用量和底物物质的量对合成L-谷氨酰正丙胺的影响。研究结果表明：温度为37 ℃、pH为10、L-谷氨酰肼浓度为0.4 mol/L,正丙胺浓度为3 mol/L,产物L-谷氨酰正丙胺的产率为97.9%,L-谷氨酰正丙胺收率为85.3%,L-谷氨酰正丙胺纯度为99.8%。谷氨酰转肽酶细胞能有效合成L-谷氨酰正丙胺。     

酿酒酵母中的谷氨酰转肽酶研究进展

介绍谷氨酰转肽酶(γ-GT)的研究概况,重点综述酿酒酵母中谷氨酰转肽酶的结构以及催化机制。酿酒酵母γ-GT在细胞中与谷胱甘肽水平的高低有密切关系,并在酵母细胞解毒或抗外界胁迫及液泡氨基酸转运的过程起着重要作用。目前,γ-GT在临床医学和工农业中有着重要的地位,并对细胞内解毒重要物质--谷胱甘肽的含量有着重要的影响。     

Development of efficient enzymatic production of theanine by γ‐glutamyltranspeptidase from a newly isolated strain of Bacillus subtilis,SK11.004

BACKGROUND: Theanine, a unique amino acid found almost exclusively in tea plants, has various favourable physiological and pharmacological functions in humans. Gamma‐glutamyltranspeptidase (GGT, EC 2.3.2.2) is considered to be the most effective enzyme for the production of theanine. In fact, GGT can catalyse the transfer of γ‐glutamyl moieties from γ‐glutamyl compounds to water (hydrolysis) or to amino acids and peptides (transpeptidation). RESULTS: A novel strain, SK11.004, which produces GGT with high theanine‐forming ability was isolated from fermented shrimp paste and identified as Bacillus subtilis through its physiological and biochemical properties as well as its 16S rDNA sequence analysis. Theanine (18.9 mmol L^?1) was synthesised by GGT (0.06 U mL^?1) through transfer reaction in the presence of glutamine (20 mmol L^?1) as a donor and ethylamine HCl (50 mmol L^?1) as an acceptor at pH 10 and 37 °C for 4 h, the conversion rate being up to 94%. CONCLUSION: The enzymatic synthesis of theanine using GGT from a newly isolated strain Bacillus subtilis SK11.004 was found to be an efficient method. Moreover, compared with others, the GGT from B. subtilis SK11.004 exhibited the highest ratio of transferring activity to hydrolytic activity using glutamine, suggesting a high potential application in the production of theanine and other functional γ‐glutamyl compounds. Copyright © 2010 Society of Chemical Industry