title: Increased L-arginine Production by Site-directed Mutagenesis of N-acetyl-L-glutamate Kinase and proB Gene Deletion in Corynebacterium crenatum.
abstract: OBJECTIVE
  In Corynebacterium crenatum, the adjacent D311 and D312 of N-acetyl-L-glutamate kinase (NAGK), as a key rate-limiting enzyme of L-arginine biosynthesis under substrate regulatory control by arginine, were initially replaced with two arginine residues to investigate the L-arginine feedback inhibition for NAGK.
  
  
  METHODS
  NAGK enzyme expression was evaluated using a plasmid-based method. Homologous recombination was employed to eliminate the proB.
  
  
  RESULTS
  The IC50 and enzyme activity of NAGK M4, in which the D311R and D312R amino acid substitutions were combined with the previously reported E19R and H26E substitutions, were 3.7-fold and 14.6% higher, respectively, than those of the wild-type NAGK. NAGK M4 was successfully introduced into the C. crenatum MT genome without any genetic markers; the L-arginine yield of C. crenatum MT-M4 was 26.2% higher than that of C. crenatum MT. To further improve upon the L-arginine yield, we constructed the mutant C. crenatum MT-M4 proB. The optimum concentration of L-proline was also investigated in order to determine its contribution to L-arginine yield. After L-proline was added to the medium at 10 mmol/L, the L-arginine yield reached 16.5 g/L after 108 h of shake-flask fermentation, approximately 70.1% higher than the yield attained using C. crenatum MT.
  
  
  CONCLUSIONS
  Feedback inhibition of L-arginine on NAGK in C. crenatum is clearly alleviated by the M4 mutation of NAGK, and deletion of the proB in C. crenatum from MT to M4 results in a significant increase in arginine production.
authors.affiliation: Key Laboratory of Functional Small Organic Molecule, Ministry of Education, and School of Life Science, Jiangxi Normal University, Nanchang 330022, Jiangxi, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Functional Small Organic Molecule, Ministry of Education, and School of Life Science, Jiangxi Normal University, Nanchang 330022, Jiangxi, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Wan
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, Jiangxi, China.
authors.forename: Yu Lou
authors.initials: YL
authors.lastname: Qiu
authors.affiliation: Key Laboratory of Functional Small Organic Molecule, Ministry of Education, and School of Life Science, Jiangxi Normal University, Nanchang 330022, Jiangxi, China.
authors.forename: Xue Lan
authors.initials: XL
authors.lastname: Chen
authors.affiliation: Key Laboratory of Functional Small Organic Molecule, Ministry of Education, and School of Life Science, Jiangxi Normal University, Nanchang 330022, Jiangxi, China.
authors.forename: Li
authors.initials: L
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, Jiangxi, China.
authors.forename: Jin Cong
authors.initials: JC
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, Jiangxi, China.
authors.forename: Yong Hua
authors.initials: YH
authors.lastname: Xiong
mesh_terms: D000818:Animals; D001120:Arginine / Q000096:biosynthesis*; D003352:Corynebacterium / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli; D025461:Feedback, Physiological; D017353:Gene Deletion; D016297:Mutagenesis, Site-Directed; D017851:Phosphotransferases (Carboxyl Group Acceptor) / Q000235:genetics*; D011392:Proline / Q000378:metabolism
chemical_list: D001120:Arginine; D011392:Proline; D017851:Phosphotransferases (Carboxyl Group Acceptor); C020650:glutamate 5-kinase; C018721:acetylglutamate kinase
keywords: Corynebacterium crenatum; L-arginine; N-acetyl-L-glutamate kinase; Site-directed mutagenesis; proB