Synthesis of Flavonoid O-Pentosides by Escherichia coli through Engineering of Nucleotide Sugar Pathways and Glycosyltransferase

摘要

Plants produce two flavonoid O -pentoses, flavonoid O -xyloside and flavonoid O -arabinoside. However, analyzing their biological properties is difficult because flavonoids are not naturally produced in sufficient quantities. In this study, Escherichia coli was used to synthesize the plant-specific flavonoid O -pentosides quercetin 3- O -xyloside and quercetin 3- O -arabinoside. Two strategies were used. First, E. coli was engineered to express components of the biosynthetic pathways for UDP-xylose and UDP-arabinose. For UDP-xylose biosynthesis, two genes, UXS (UDP-xylose synthase) from Arabidopsis thaliana and ugd (UDP-glucose dehydrogenase) from E. coli , were overexpressed. In addition, the gene encoding ArnA (UDP-l-Ara4N formyltransferase/UDP-GlcA C-4″-decarboxylase), which competes with UXS for UDP-glucuronic acid, was deleted. For UDP-arabinose biosynthesis, UXE (UDP-xylose epimerase) was overexpressed. Next, we engineered UDP-dependent glycosyltransferases (UGTs) to ensure specificity for UDP-xylose and UDP-arabinose. The E. coli strains thus obtained synthesized approximately 160 mg/liter of quercetin 3- O -xyloside and quercetin 3- O -arabinoside.