Abstract
BackgroundNucleotide 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.ResultsFour 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.ConclusionsWe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0582-8) contains supplementary material, which is available to authorized users.
Highlights
Nucleotide sugars serve as sugar donors for the synthesis of various glycones
uridine diphosphate (UDP)-rhamnose is synthesized from UDP-glucose by one multifunctional enzyme whereas in bacteria, TDP-rhamnose is synthesized from TDP-glucose in three steps by three different enzymes [10]
Introduction of two genes (Pdeg and Preq) for the biosynthesis of UDP-N-acetylquinovosamine into E. coli could lead to the synthesis of a new Plasmids or E. coli strain Relevant properties or genetic marker
Summary
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. Attachment of diverse sugar molecules to secondary metabolites such as antibiotics and phytochemicals is of interest because the biological activities of glycones are often modulated by sugar molecules [1,2,3,4]. Flavonoids, a major group of phytochemicals, are synthesized using the phenylpropanoid pathway [5]. Attachment of sugars to flavonoids is mediated. UDP-rhamnose is synthesized from UDP-glucose by one multifunctional enzyme (rhamnose synthase, RHM) whereas in bacteria, TDP-rhamnose is synthesized from TDP-glucose in three steps by three different enzymes [10]
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