@article { ISI:000313165500067, title = {Functional characterization, homology modeling and docking studies of beta-glucosidase responsible for bioactivation of cyanogenic hydroxynitrile glucosides from Leucaena leucocephala (subabul)}, journal = {Molecular Biology Reports}, volume = {40}, number = {2}, year = {2013}, month = {FEB}, pages = {1351-1363}, publisher = {SPRINGER}, address = {VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS}, abstract = {

Glycosyl hydrolase family 1 beta-glucosidases are important enzymes that serve many diverse functions in plants including defense, whereby hydrolyzing the defensive compounds such as hydroxynitrile glucosides. A hydroxynitrile glucoside cleaving beta-glucosidase gene (Llbglu1) was isolated from Leucaena leucocephala, cloned into pET-28a (+) and expressed in E. coli BL21 (DE3) cells. The recombinant enzyme was purified by Ni-NTA affinity chromatography. The optimal temperature and pH for this beta-glucosidase were found to be 45 A degrees C and 4.8, respectively. The purified Llbglu1 enzyme hydrolyzed the synthetic glycosides, pNPGlucoside (pNPGlc) and pNPGalactoside (pNPGal). Also, the enzyme hydrolyzed amygdalin, a hydroxynitrile glycoside and a few of the tested flavonoid and isoflavonoid glucosides. The kinetic parameters K (m) and V (max) were found to be 38.59 mu M and 0.8237 mu M/mg/min for pNPGlc, whereas for pNPGal the values were observed as 1845 mu M and 0.1037 mu M/mg/min. In the present study, a three dimensional (3D) model of the Llbglu1 was built by MODELLER software to find out the substrate binding sites and the quality of the model was examined using the program PROCHEK. Docking studies indicated that conserved active site residues are Glu 199, Glu 413, His 153, Asn 198, Val 270, Asn 340, and Trp 462. Docking of rhodiocyanoside A with the modeled Llbglu1 resulted in a binding with free energy change (Delta G) of -5.52 kcal/mol on which basis rhodiocyanoside A could be considered as a potential substrate.

}, keywords = {Glycosyl hydrolase family 1, homology modeling, Leucaena leucocephala, Molecular docking}, issn = {0301-4851}, doi = {10.1007/s11033-012-2179-6}, author = {Shaik, Noor M. and Misra, Anurag and Singh, Somesh and Fatangare, Amol B. and Ramakumar, Suryanarayanarao and Rawal, Shuban K. and Khan, Bashir Mohammad} } @article { ISI:000319134800020, title = {Functional characterization of a flavonoid glycosyltransferase gene from withania somnifera (Ashwagandha)}, journal = {Applied Biochemistry and Biotechnology}, volume = {170}, number = {3}, year = {2013}, month = {JUN}, pages = {729-741}, publisher = {HUMANA PRESS INC}, address = {999 RIVERVIEW DRIVE SUITE 208, TOTOWA, NJ 07512 USA}, abstract = {

Glycosylation of flavonoids is mediated by family 1 uridine diphosphate (UDP)-dependent glycosyltransferases (UGTs). Until date, there are few reports on functionally characterized flavonoid glycosyltransferases from Withania somnifera. In this study, we cloned the glycosyltransferase gene from W. somnifera (UGT73A16) showing 85-92 \% homology with UGTs from other plants. UGT73A16 was expressed as a His(6)-tagged fusion protein in Escherichia coli. Several compounds, including flavonoids, were screened as potential substrates for UGT73A16. HPLC analysis and hypsochromic shift indicated that UGT73A16 transfers a glucose molecule to several different flavonoids. Based on kinetic parameters, UGT73A16 shows more catalytic efficiency towards naringenin. Here, we explored UGT73A16 of W. somnifera as whole cell catalyst in E. coli. We used flavonoids (genistein, apigenin, kaempferol, naringenin, biochanin A, and daidzein) as substrates for this study. More than 95 \% of the glucoside products were released into the medium, facilitating their isolation. Glycosylation of substrates occurred on the 7- and 3-hydroxyl group of the aglycone. UGT73A16 also displayed regiospecific glucosyl transfer activity towards 3-hydroxy flavone compound, which is the backbone of all flavonols and also for a chemically synthesized compound, not found naturally. The present study generates essential knowledge and molecular as well as biochemical tools that allow the verification of UGT73A16 in glycosylation.

}, keywords = {Flavonoid, glycosylation, Glycosyltransferase, Hypsochromic shift, Plant secondary product glycosyltransferase (PSPG), Withania somnifera}, issn = {0273-2289}, doi = {10.1007/s12010-013-0230-2}, author = {Singh, Somesh and Vishwakarma, Rishi. K. and Kumar, R. J. Santosh and Sonawane, Prashant D. and Ruby and Khan, Bashir Mohammad} } @article { ISI:000323669900005, title = {Functional characterization of a glucosyltransferase specific to flavonoid 7-O-glucosides from withania somnifera}, journal = {Plant Molecular Biology Reporter}, volume = {31}, number = {5}, year = {2013}, month = {OCT}, pages = {1100-1108}, publisher = {SPRINGER}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Flavonoids are a large class of phenylpropanoid-derived secondary metabolites, which are usually glycosylated by UDP-glycosyltransferases with one or more sugar groups. Here, we report the cloning and biochemical characterization of a flavonoid glycosyltransferase gene from Withania somnifera (WsGT), which is an important medicinal plant used in Ayurvedic formulations. Using PCR primers, designed for a highly conserved region of previously reported glycosyltransferases, we were able to isolate the corresponding fragment of the WsGT gene. Rapid amplification of cDNA ends (RACE) was then employed to isolate full-length cDNA, which had an open reading frame of 1,371 bp that encode for 456 amino acids. Phylogenetic analysis indicated that WsGT was similar to that of family 1 GT-B glycosyltransferase. Biochemical analysis revealed that WsGT interacts with UDP-glucose and was capable of regiospecifically glycosylating flavonoid-7-ols, such as apigenin, naringenin, luteolin, diadzein and genistein. Expression profiling studies showed that WsGT was highly expressed in young and mature leaves of W. somnifera. Furthermore, exposure to salicylic acid enhanced the expression of WsGT in the leaves and heat shock treatment resulted in decreased expression of WsGT after an initial increase. This may suggest the role of WsGT in response to abiotic/biotic stresses.

}, keywords = {Diadzein, Flavonoids, Glycosyltransferase, Withania somnifera}, issn = {0735-9640}, doi = {10.1007/s11105-013-0573-4}, author = {Kumar, R. J. Santosh and Ruby and Singh, Somesh and Sonawane, Prashant D. and Vishwakarma, R. K. and Khan, Bashir Mohammad} }