title: Regiospecific modifications of naringenin for astragalin production in Escherichia coli.
abstract: We report the production of astragalin (AST) from regiospecific modifications of naringenin (NRN) in Escherichia coli BL21(DE3). The exogenously supplied NRN was converted into dihydrokaempferol (DHK) and then kaempferol (KMF) in the presence of flavanone-3-hydroxylase (f3h) and flavonone synthase (fls1) from Arabidopsis thaliana, respectively. KMF was further modified to produce AST by 3-O-glucosylation utilizing the endogeneous UDP-glucose in presence of UGT78K1 from Glycine max. To increase the intracellular UDP-glucose concentration by channeling the carbon flux toward UDP-glucose at the branch point of glucose-6-phosphate (G6P), the chromosomal glucose phosphate isomerase (pgi) and D-glucose-6-phosphate dehydrogenase (zwf) were knocked-out in E. coli BL21(DE3). The two enzymes directly involved in the synthesis of UDP-glucose from G6P, phosphoglucomutase (nfa44530) from Nocardia farcinia and glucose-1-phosphate uridylyltransferase (galU) from E. coli K12 were overexpressed, which successfully diverted the carbon flow from glycolysis to the synthesis of UDP-glucose. Furthermore, to prevent the dissociation of UDP-glucose into UDP and glucose, the UDP-glucose hydrolase (ushA) was deleted. The E. coli ΔpgiΔzwfΔushA mutant harboring the UDP-glucose biosynthetic pathway and the aforementioned genes for the regiospecific glucosylation produced 109.3 mg/L (244 µM) of AST representing 48.8% conversion from 500 µM of NRN in 60 h without any supplementation of extracellular UDP-glucose.
authors.affiliation: Laboratory of Molecular Biotechnology and Biomaterials, School of Chemical and Biological Engineering, Seoul National University, Seoul, South Korea.
authors.forename: Sailesh
authors.initials: S
authors.lastname: Malla
authors.forename: Ramesh Prasad
authors.initials: RP
authors.lastname: Pandey
authors.forename: Byung-Gee
authors.initials: BG
authors.lastname: Kim
authors.forename: Jae Kyung
authors.initials: JK
authors.lastname: Sohng
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics; D019149:Bioreactors; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005285:Fermentation; D044950:Flavanones / Q000737:chemistry* / Q000378:metabolism; D005419:Flavonoids; D044949:Kaempferols / Q000032:analysis / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D029681:Arabidopsis Proteins; D044950:Flavanones; D005419:Flavonoids; D044949:Kaempferols; D011994:Recombinant Proteins; C001579:astragalin; D006899:Mixed Function Oxygenases; C005273:naringenin
keywords: E. coli; flavonoids; glycosylation; heterologous expression; kaempferol-3-O-glucoside