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Rit Bahadur Gurung,송재경,김은희,오태진 한국분자세포생물학회 2013 Molecules and cells Vol.36 No.4
Apigenin, a member of the flavone subclass of flavono-ids, has long been considered to have various biological activities. Its glucosides, in particular, have been reported to have higher water solubility, increased chemical stability, and enhanced biological activities. Here, the synthesis of apigenin glucosides by the in vitro glucosylation reaction was successfully performed using a UDP-glucosyltrans-ferase YjiC, from Bacillus licheniformis DSM 13. The glucosylation has been confirmed at the phenolic groups of C-4′ and C-7 positions ensuing apigenin 4′-O-glucoside, apigenin 7-O-glucoside and apigenin 4′,7-O-diglucoside as the products leaving the C-5 position unglucosylated. The position of glucosylation and the chemical structures of glucosides were elucidated by liquid chromatography/ mass spectroscopy and nuclear magnetic resonance spec- troscopy. The parameters such as pH, UDP glucose concentration and time of incubation were also analyzed during this study.
( Rit Bahadur Gurung ),( So Youn Gong ),( Dipesh Dhakal ),( Tuoi Thi Le ),( Na Rae Jung ),( Hye Jin Jung ),( Tae Jin Oh ),( Jae Kyung Sohng ) 한국미생물생명공학회(구 한국산업미생물학회) 2017 Journal of microbiology and biotechnology Vol.27 No.9
Curcumin is a natural polyphenolic compound, widely acclaimed for its antioxidant, antiinflammatory, antibacterial, and anticancerous properties. However, its use has been limited due to its low-aqueous solubility and poor bioavailability, rapid clearance, and low cellular uptake. In order to assess the effect of glycosylation on the pharmacological properties of curcumin, one-pot multienzyme (OPME) chemoenzymatic glycosylation reactions with UDP- α-D-glucose or UDP-α-D-2-deoxyglucose as donor substrate were employed. The result indicated significant conversion of curcumin to its glycosylated derivatives: curcumin 4`-O-β- glucoside, curcumin 4`,4``-di-O-β-glucoside, curcumin 4`-O-β-2-deoxyglucoside, and curcumin 4`,4``-di-O-β-2-deoxyglucoside. The products were characterized by ultra-fast performance liquid chromatography, high-resolution quadruple-time-of-flight electrospray ionization-mass spectrometry, and NMR analyses. All the products showed improved water solubility and comparable antibacterial activities. Additionally, the curcumin 4`-O-β-glucoside and curcumin 4`-O-β-2-deoxyglucoside showed enhanced anticancer activities compared with the parent aglycone and diglycoside derivatives. This result indicates that glycosylation can be an effective approach for enhancing the pharmaceutical properties of different natural products, such as curcumin.
In-vitro glycosylation of apigenin by YjiC from Bacillus licheniformis
Rit Bahadur Gurung,Kiran Upreti,Jae Kyung Sohng 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1
The glycosylation process helps in stabilization, detoxification and solubilization of many compounds. Apigenin, which is a class of flavonoid, known for its high antioxidant activity and contains hydroxyl groups at C-5, C-7 and C-4' positions, has been glycosylated using YjiC, a glycosyltransferase obtained from Bacillus licheniformis DSM 13, which is an industrial organism used for the manufacture of enzymes, antibiotics, and chemicals. YjiC consists of 1,191 bp open reading frame encoding a 44.7 kDa protein. UDP-D-glucose has been used as a sugar donor. Thin layer chromatography (TLC), high-performance liquid chromatography (HPLC) and electrospray ionization tandem mass spectorscopy (ESI-MS-MS) analyses of in-vitro reaction products revealed that YjiC could glycosylate apigenin. The positon of glycosylation in apigenin is yet to be determined.
Rit Bahadur Gurung,Jae Kyung Sohng 한국당과학회 2013 한국당과학회 학술대회 Vol.2013 No.1
Glycosylation can significantly improve the water solubility, stability and thus increase bioavailability and enhance biological activity of low molecular weight organic compounds. Enzymatic glycosylation methods have several advantages over the classical methods of organic syntheses in terms of cost, efficiency and selectivity. The UDP-glucosyltransferase YjiC from Bacillus licheniformis DSM 13, a member of family 1 glycosyltransferase was expressed in Escherichia coli BL21 (DE3) as N-terminal hexahistidine-tagged fusion protein. Purified YjiC was used to glycosylate apigenin, baicalein, chrysin, diosmetin and luteolin. The products have been analyzed by high performance liquid chromatography (HPLC) and high resolution liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry (HRLC-ESI-Q-TOF-MS) methods. The formation of mono and diglucosides has been reported with all the substrates. Even though glycosylation is preferred at positions other than C5 carbon of flavonoids whenever there is the presence of more than one phenolic hydroxyl groups, the promiscuity of YjiC was not observed. The exact position of glycosylation by YjiC is yet to be determined.
Glycosylation of small molecules: generation of novel pharmaceutical compounds for future drug use
Ramesh Prasad Pandey,Rit Bahadur Gurung,Prakash Parajuli,Jae Kyung Sohng 한국당과학회 2013 한국당과학회 학술대회 Vol.2013 No.1
The biological activity of many natural products and pharmaceutically used drugs are attributed by the glycosidic residues attached to it. Generally, the glycosylation determines the competence of the most of the molecules as a drug. Therefore, engineering the sugar moiety in the natural products is one of the most efficient ways of generating novel compounds with diverse pharmacological properties. The screening and engineering of flexible glycosyltransferases from different sources and applying those enzymes for the biosynthesis of novel small molecule glycosides is still significantly demanding. In this context, we have identified a novel glycosyltransferase (YjiC) from Bacillus licheniformis and applied to glycosylate small molecule natural products like, flavonoids, isoflavonoids, chalcones, stillbenes, curcuminoids etc. The substrate flexibility of thus identified glycosyltaransferase is found to have broad, which resulted to generate a number of natural product glycosides including novel compounds. The enzyme glycosylates non-regiospecifically at suitable hydroxyl groups to produce O-glucosides of compounds. Moreover, this glycosyltransferase has shown flexibility towards NDP-sugar donors. This property of the enzyme would help to engineer the sugar moiety of most of the small molecules which might exhibit potentially different biological activities. The exchange of sugar moiety might help to modulate the biological application of the parent bioactive compounds. Plenty of biologically active aglycones and their glycoside derivatives are characterized to have diverse biological activities against wide-range of diseases. The production of such pharmaceutically important glycoside compounds and their glyco-engineering to alter biological function would be noteworthy in scientific world to develop a novel drug for future use.