title: Biosynthesis of three N-acetylaminosugar-conjugated flavonoids using engineered Escherichia coli.
abstract: BACKGROUND
  Nucleotide sugars serve as sugar donors for the synthesis of various glycones. The biological and chemical properties of glycones can be altered depending which sugar is attached. Bacteria synthesize unusual nucleotide sugars. A novel nucleotide sugar can be synthesized in Escherichia coli by introducing nucleotide biosynthetic genes from other microorganisms into E. coli. The engineered E. coli strains can be used as a platform for the synthesis of novel glycones.
  
  
  RESULTS
  Four genes, Pdeg (UDP-N-acetylglucosamine C4,6-dehydratase), Preq (UDP-4-reductase), UDP-GlcNAc 6-DH (UDP-N-acetylglucosamine 6-dehydrogenase), and UXNAcS (UDP-N-acetylxylosamine synthase), were employed to synthesize UDP-quinovosamine, UDP-N-acetylglucosaminuronic acid, and UDP-N-acetylxylosamine in E. coli. We engineered an E. coli nucleotide sugar biosynthetic pathway to increase the pool of substrate for the target nucleotide sugars. Uridine diphosphate dependent glycosyltransferase (UGT) was also selected and introduced into E. coli. Using engineered E. coli, high levels of three novel flavonoid glycosides were obtained; 158.3 mg/L quercetin 3-O-(N-acetyl)quinovosamine, 172.5 mg/L luteolin 7-O-(N-acetyl)glucosaminuronic acid, and 160.8 mg/L quercetin 3-O-(N-acetyl)xylosamine.
  
  
  CONCLUSIONS
  We reconstructed an E. coli nucleotide pathway for the synthesis of UDP-quinovosamine, UDP-N-acetylglucosaminuronic acid and UDP-N-acetylxylosamine in an E. coli galU (UDP-glucose 1-phosphate uridylyltransferase) or pgm (phosphoglucomutase) deletion mutant. Using engineered E. coli strains harboring a specific UGT, three novel flavonoids glycones were synthesized. The E. coli strains used in this study can be used for the synthesis of diverse glycones.
authors: Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, 143-701, South Korea.
authors: A Ra
authors: AR
authors: Cho
authors: Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, 143-701, South Korea.
authors: Su Jin
authors: SJ
authors: Lee
authors: Department of Forest Resources, Gyeongnam National University of Science and Technology, 33 Dongjin-ro, Jinju, Gyeongsangman-do, 660-758, South Korea.
authors: Bong Gyu
authors: BG
authors: Kim
authors: Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, 143-701, South Korea. jhahn@konkuk.ac.kr.
authors: Joong-Hoon
authors: JH
authors: Ahn
mesh_terms: D000606:Amino Sugars / Q000096:biosynthesis*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D005419:Flavonoids / Q000096:biosynthesis*; D060847:Metabolic Engineering / Q000379:methods
chemical_list: D000606:Amino Sugars; D005419:Flavonoids
keywords: Glycosyltransferase; Metabolic engineering; Nucleotide sugars