title: Systematic manipulation of glutathione metabolism in Escherichia coli for improved glutathione production.
abstract: BACKGROUND
  L-glutathione (GSH) is a non-protein thiol compound with important biological properties and is widely used in pharmaceutical, food, cosmetic and health products. The cellular GSH is determined by the activity and characteristic of GSH-synthesizing enzymes, energy and precursor supply, and degradation of formed GSH.
  
  
  RESULTS
  In this study, genes encoding enzymes related to the precursor amino acid degradation and glycogen formation as well as GSH degradation were systematically manipulated in Escherichia coli strains over-expressing gshF from Actinobacillus succinogenes. The manipulation included disrupting the precursor degradation pathways (tnaA and sdaA), eliminating L-glutathione degradation (ggt and pepT), and manipulating the intracellular ATP level (disruption of glgB). However the constructed mutants showed lower levels of GshF expression. 2-D electrophoresis was performed to elucidate the reasons for this discrepancy, and the results indicated obvious changes in central metabolism and amino acid metabolism in the penta-mutant. Fed-batch culture of the penta-mutant ZJ12345 was performed where the GshF expression level was enhanced, and both the GSH production (19.10 mM) and the yield based on added L-cysteine (0.76 mmol/mmol) were significantly increased.
  
  
  CONCLUSIONS
  By interrupting the degradation pathways of L-cysteine, serine and GSH and blocking glycogen formation, the GSH production efficiency was significantly improved.
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China. 18818200302@163.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China. 727342366@qq.com.
authors.forename: Cong
authors.initials: C
authors.lastname: Quan
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China. wangcheng15854584437@126.com.
authors.forename: Cheng
authors.initials: C
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China. hwu@ecust.edu.cn.
authors.forename: Hui
authors.initials: H
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China. lizm@ecust.edu.cn.|Shanghai Collaborative Innovation Center for Biomanufacturing Technology, 130 Meilong Road, Shanghai, 200237, China. lizm@ecust.edu.cn.
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China. qye@ecust.edu.cn.
authors.forename: Qin
authors.initials: Q
authors.lastname: Ye
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D061249:Batch Cell Culture Techniques; D055162:Biocatalysis / Q000187:drug effects; D003545:Cysteine / Q000378:metabolism; D004734:Energy Metabolism / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D005285:Fermentation / Q000187:drug effects; D055786:Gene Knockout Techniques; D005978:Glutathione / Q000096:biosynthesis*; D005981:Glutathione Synthase / Q000378:metabolism; D013058:Mass Spectrometry; D060847:Metabolic Engineering / Q000379:methods*; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D040901:Proteomics
chemical_list: D029968:Escherichia coli Proteins; D000255:Adenosine Triphosphate; D005981:Glutathione Synthase; D005978:Glutathione; D003545:Cysteine