title: Glutamate dehydrogenase (RocG) in Bacillus licheniformis WX-02: Enzymatic properties and specific functions in glutamic acid synthesis for poly-γ-glutamic acid production.
abstract: Poly-γ-glutamic acid (γ-PGA), a natural biopolymer, is widely used in cosmetics, medicine, food, water treatment, and agriculture owing to its features of moisture sequestration, cation chelation, non-toxicity and biodegradability. Intracellular glutamic acid, the substrate of γ-PGA, is a limiting factor for high yield in γ-PGA production. Bacillus subtilis and Bacillus licheniformis are both important γ-PGA producing strains, and B. subtilis synthesizes glutamic acid in vivo using the unique GOGAT/GS pathway. However, little is known about the glutamate synthesis pathway in B. licheniformis. The aim of this work was to characterize the glutamate dehydrogenase (RocG) in glutamic acid synthesis from B. licheniformis with both in vivo and in vitro experiments. By re-directing the carbon flux distribution, the rocG gene deletion mutant WX-02ΔrocG produced intracellular glutamic acid with a concentration of 90ng/log(CFU), which was only 23.7% that of the wild-type WX-02 (380ng/log(CFU)). Furthermore, the γ-PGA yield of mutant WX-02ΔrocG was 5.37g/L, a decrease of 45.3% compared to the wild type (9.82g/L). In vitro enzymatic assays of RocG showed that RocG has higher affinity for 2-oxoglutarate than glutamate, and the glutamate synthesis rate was far above degradation. This is probably the first study to reveal the glutamic acid synthesis pathway and the specific functions of RocG in B. licheniformis. The results indicate that γ-PGA production can be enhanced through improving intracellular glutamic acid synthesis.
authors.affiliation: School of Animal Science, Yangtze University, Jingzhou 434025, People's Republic of China; Hubei Key Laboratory of Waterlogging Disaster and Agriculture Use of Wetland, Yangtze University, Jingzhou 434025, People's Republic of China.
authors.forename: Guangming
authors.initials: G
authors.lastname: Tian
authors.affiliation: Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, College of Life Sciences, Hubei University, Wuhan 430062, People's Republic of China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Wang
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, People's Republic of China.
authors.forename: Xuetuan
authors.initials: X
authors.lastname: Wei
authors.affiliation: Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, College of Life Sciences, Hubei University, Wuhan 430062, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Ma
authors.affiliation: Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, College of Life Sciences, Hubei University, Wuhan 430062, People's Republic of China. Electronic address: shouw_chen@126.com.
authors.forename: Shouwen
authors.initials: S
authors.lastname: Chen
mesh_terms: D000069976:Bacillus licheniformis / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D053898:Biosynthetic Pathways; D017353:Gene Deletion; D055786:Gene Knockout Techniques; D005798:Genes, Bacterial; D005969:Glutamate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D005970:Glutamate Synthase / Q000378:metabolism; D018698:Glutamic Acid / Q000096:biosynthesis; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology; D007700:Kinetics; D009154:Mutation; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D018698:Glutamic Acid; C107166:glutamate synthase A; D005970:Glutamate Synthase; D005969:Glutamate Dehydrogenase
keywords: Bacillus licheniformis; Enzymatic property; Glutamate dehydrogenase; Glutamate synthesis; Poly-γ-glutamic acid