title: Intracellular synthesis of glutamic acid in Bacillus methylotrophicus SK19.001, a glutamate-independent poly(γ-glutamic acid)-producing strain.
abstract: BACKGROUND
  Bacillus methylotrophicus SK19.001 is a glutamate-independent strain that produces poly(γ-glutamic acid) (γ-PGA), a polymer of D- and L-glutamic acids that possesses applications in food, the environment, agriculture, etc. This study was undertaken to explore the synthetic pathway of intracellular L- and D-glutamic acid in SK19.001 by investigating the effects of tricarboxylic acid cycle intermediates and different amino acids as metabolic precursors on the production of γ-PGA and analyzing the activities of the enzymes involved in the synthesis of L- and D-glutamate.
  
  
  RESULTS
  Tricarboxylic acid cycle intermediates and amino acids could participate in the synthesis of γ-PGA via independent pathways in SK19.001. L-Aspartate aminotransferase, L-glutaminase and L-glutamate synthase were the enzymatic sources of L-glutamate. Glutamate racemase was responsible for the formation of D-glutamate for the synthesis of γ-PGA, and the synthetase had stereoselectivity for glutamate substrate.
  
  
  CONCLUSIONS
  The enzymatic sources of L-glutamate were investigated for the first time in the glutamate-independent γ-PGA-producing strain, and multiple enzymatic sources of L-glutamate were verified in SK19.001, which will benefit efforts to improve production of γ-PGA with metabolic engineering strategies.
authors.affiliation: State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry & Biotechnology, Jiangnan University, Wuxi, Jiangsu, 214122, China.|School of Chemical and Biological Engineering, Yancheng Institute of Technology, Yancheng, Jiangsu 22400, China.
authors.forename: Yingyun
authors.initials: Y
authors.lastname: Peng
authors.affiliation: State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry & Biotechnology, Jiangnan University, Wuxi, Jiangsu, 214122, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry & Biotechnology, Jiangnan University, Wuxi, Jiangsu, 214122, China.
authors.forename: Wanmeng
authors.initials: W
authors.lastname: Mu
authors.affiliation: State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry & Biotechnology, Jiangnan University, Wuxi, Jiangsu, 214122, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Miao
authors.affiliation: State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry & Biotechnology, Jiangnan University, Wuxi, Jiangsu, 214122, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Jiang
mesh_terms: D000591:Amino Acid Isomerases / Q000378:metabolism; D001219:Aspartate Aminotransferases / Q000378:metabolism; D001407:Bacillus / Q000201:enzymology / Q000378:metabolism*; D002952:Citric Acid Cycle; D003593:Cytoplasm / Q000378:metabolism; D005285:Fermentation; D005970:Glutamate Synthase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D005972:Glutaminase / Q000378:metabolism; D006801:Humans; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis; D013379:Substrate Specificity
chemical_list: C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D018698:Glutamic Acid; D005970:Glutamate Synthase; D001219:Aspartate Aminotransferases; D005972:Glutaminase; D000591:Amino Acid Isomerases; C062292:glutamate racemase
keywords: Bacillus methylotrophicus SK19.001; glutamate racemase; l-glutamate sources; poly(γ-glutamic acid)