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Study of C-Glycosylation of selected Flavones
Anil Shrestha,Vijay Rayamaihi,Dipesh Dhakal,Jae Kyung Sohng 한국당과학회 2017 한국당과학회 학술대회 Vol.2017 No.01
Glycosylation reactions are widespread in nature, and involved almost all vital processes. Glycosylated compounds directly exert a wide range of functions, including energy storage, maintenance of the cellular integrity, information storage and transfer, molecular recognition, cell-cell interaction, cellular regulation, virulence and chemical defense. Glycosylated compounds are the most structurally diverse biomolecules, and their biosynthesis needs quite complex biological processes orchestrated by many enzyme systems. In Plants, various natural products are produced including diverse flavonoid derivatives. Mostly these metabolites are generally glycosides and are accumulated in the vacuole. Among C-glycosylflavones, comprising the various pharmacological activities, are biosynthesized from flavone via C-glycosylation of 2-hydroxyflavone or flavone. This is mediated by uridine diphosphate (UDP)-sugar dependent glycosyltransferase. The C-glycosyltransferase catalyzes the transfer of the glucose moiety to the aromatic carbon of the acceptor substrate. C-Glycosylflavones are involved in UV protection, defense against pathogens and inhibition of caterpillar growth. In this study, we tried to biosynthesize C-glycosylflavone in vivo and the product was confirmed by LC-MS.
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Production of C-glycosylated flavones by metabolic engineering in E. coli
Anil Shrestha,Dipesh Dhakal,Ramesh Prasad Pandey,Jae Kyung Sohng 한국당과학회 2018 한국당과학회 학술대회 Vol.2018 No.01
Generally glycosylated natural compounds have the specific contribution to the pharmacological properties. Particularly, C-glycosylflavones are involved in UV protection, defense against pathogens and inhibition of caterpillar growth. C-glycosylflavones are biosynthesized from flavone via C-glycosylation of 2-hydroxyflavone or flavone. Two plant C-glucosyltransferases (CGTs) UGT708D1 from Glycine max and GtUF6CGT1 from Gentian triflora were used for glucosylation of chrysin. UDP-glucose pool was enhanced by introducing heterologous UDP-glucose biosynthestic genes i.e., glucokinase (glk), phosphoglucomutase (pgm2), and glucose 1-phosphate uridylyltransferase (galU), along with glucose facilitator diffusion protein (glf), in a multi-monocistronic vector pIBR. Moreover, the bioengineered E. coli strains enhanced the production by approximately 1.4–fold, thus producing 10 mg/L and 14 mg/L by UGT708D1 and GtUF6CGT1, respectively, without supplementation of additional UDP-glucose in the medium. HPLC analysis of fermentation broth extract showed 50 % (42 mg/L) conversion. Thus in this study, we successfully biosynthesized C-glycosylflavone in vivo and the product was confirmed by LC-MS and NMR.
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Enzymatic and Microbial Biosynthesis of Natural Products Glycosides
Ramesh Prasad Pandey,PrakashParajuli,AnilShrestha,JaeKyungSohng 한국당과학회 2018 한국당과학회 학술대회 Vol.2018 No.07
Post-biosynthesis modifications of natural products (NPs) provides opportunity to bring chemical diversity to the parent molecule. Such modifications usually play vital roles in executing biological activities of the molecules. Thus, engineering of molecules by diverse post-modifications is increasingly becoming a tool to design or produce novel biologically potent biologics. To develop the rapid and sustainable system for the production of different flavonoid glycosides, central metabolic pathway for the production of pool of UDP-0-glucose, UDP-0-xylose, TDP-L -rhamnose, TDP-0-viosamine, TOP 4-amino 4,6-dideoxy-D-galactose, and TOP 3-amino 3,6-dideoxy-D-galactose was engineered in E. coli BL21 (DE3) cells. Different glycosyltransferases were engaged to transfer sugar moieties to aglycones. Several flavonoids and isoflavonoid glycosides including natural and non-natural o- and C- glycosides were produced by microbial cell fermentation. In a different approach of enzymatic biosynthesis, a number of glycodiversified flavonoids were generated using several NDP-sugars and GTs in vitro. As a result, glycodiversified resveratrol, flavonol, epothilone A, mupirocin conjugated with glucose, galactose, 2-deoxyglucose, viosamine, rhamnose, and fucose sugars were produced. Multiple glycosides of other flavonoids, isoflavonoids, chalcones, stilbenes, xanthonoids, anthraquinones, anthracyclines, and terpenoids were also generated with significantly high yield. Some of the selected glycosides exhibited promising anticancer, antibacterial, immunomodulatory, anti-inflammatory, antioxidant, and anti-asthmatic activities in in vitro and in vivo mouse models. This approach of microbial and enzymatic synthesis of novel glycosides derivatives of NPs using highly flexible and promiscuous enzymes from diverse sources opened up possibility of development of new molecules with better stability, bioavailability, and novel biological activity.
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