JBA-07035; No of Pages 26 Biotechnology Advances xxx (2016) xxx–xxx Contents lists available at ScienceDirect Biotechnology Advances journal homepage: www.elsevier.com/locate/biotechadv Research review paper Plant secondary metabolism linked glycosyltransferases: An update on expanding knowledge and scopes Pragya Tiwari a, Rajender Singh Sangwan a,b,NeelamS.Sangwana,⁎ a Department of Metabolic and Structural Biology, CSIR-Central Institute of Medicinal and Aromatic Plants (CSIR-CIMAP), P.O. CIMAP, Lucknow 226015,India b Center of Innovative and Applied Bioprocessing (CIAB), A National Institute under Department of Biotechnology, Government of India, C-127, Phase-8, Industrial Area, S.A.S. Nagar, Mohali 160071, Punjab, India article info abstract Article history: The multigene family of enzymes known as glycosyltransferases or popularly known as GTs catalyze the addition Received 6 October 2015 of carbohydrate moiety to a variety of synthetic as well as natural compounds. Glycosylation of plant secondary Received in revised form 6 February 2016 metabolites is an emerging area of research in drug designing and development. The unsurpassing complexity Accepted 19 March 2016 and diversity among natural products arising due to glycosylation type of alterations including Available online xxxx glycodiversification and glycorandomization are emerging as the promising approaches in pharmacological stud- ies. While, some GTs with broad spectrum of substrate specificity are promising candidates for glycoengineering Keywords: fi Catalytic mechanism while others with stringent speci city pose limitations in accepting molecules and performing catalysis. With the Drug designing rising trends in diseases and the efficacy/potential of natural products in their treatment, glycosylation of plant Glycoconjugates secondary metabolites constitutes a key mechanism in biogeneration of their glycoconjugates possessing medic- Glycosyltransferases inal properties. The present review highlights the role of glycosyltransferases in plant secondary metabolism Metabolic engineering with an overview of their identification strategies, catalytic mechanism and structural studies on plant GTs. Fur- Plant secondary metabolism thermore, the article discusses the biotechnological and biomedical application of GTs ranging from detoxifica- tion of xenobiotics and hormone homeostasis to the synthesis of glycoconjugates and crop engineering. The future directions in glycosyltransferase research should focus on the synthesis of bioactive glycoconjugates via metabolic engineering and manipulation of enzyme's active site leading to improved/desirable catalytic proper- ties. The multiple advantages of glycosylation in plant secondary metabolomics highlight the increasing signifi- cance of the GTs, and in near future, the enzyme superfamily may serve as promising path for progress in expanding drug targets for pharmacophore discovery and development. © 2016 Published by Elsevier Inc. Contents 1. Introduction............................................................... 0 1.1. Plantsecondarymetaboliteglycosylationmetabolism:anintroduction................................. 0 2. Plantsecondarymetabolismglycosyltransferases:anoverview........................................ 0 3. PlantGTsinCAZYdatabase........................................................ 0 4. IdentificationandisolationofGTs..................................................... 0 4.1. Transcriptomicsand/ormetabolomicsstrategies........................................... 0 4.2. FunctionalanalysisofUGTgenesthroughclassicalapproaches..................................... 0 4.3. Bioinformaticstudies....................................................... 0 4.4. Biochemicalmethods....................................................... 0 4.5. Molecularbiologystudies..................................................... 0 5. Kineticparametersofcatalysisandsubstratepreferences.......................................... 0 6. Family1GTs:themechanismofcatalysis................................................. 0 7. Crystalstructureofglycosyltransferases.................................................. 0 Abbreviations: GTs, glycosyltransferases; PSPG, plant secondary product glycosyltransferases; UGT, UDP dependent glycosyltransferase; TOGT, Tobacco-O-glucosyltransferase; ATTED- II, database of gene coexpression in Arabidopsis; AtUGT72B1, Arabidopsis thaliana UGT72B1; MtUGT71G1, Medicago truncatula UGT71G1; MtUGT85H2, Medicago truncatula UGT85H2; VvGT1, Vitis vinifera flavonoid 3-O-glucosyltransferase; vvUFGT, Vitis vinifera anthocyanidin glucosyltransferase. ⁎ Corresponding author. E-mail addresses: [email protected], [email protected] (N.S. Sangwan). http://dx.doi.org/10.1016/j.biotechadv.2016.03.006 0734-9750/© 2016 Published by Elsevier Inc. Please cite this article as: Tiwari, P., et al., Plant secondary metabolism linked glycosyltransferases: An update on expanding knowledge and scopes, Biotechnol Adv (2016), http://dx.doi.org/10.1016/j.biotechadv.2016.03.006 2 P. Tiwari et al. / Biotechnology Advances xxx (2016) xxx–xxx 7.1. GT-Afamily............................................................ 0 7.2. GT-Bfamily............................................................ 0 8. 3Dstructureofplantglycosyltransferases.................................................. 0 8.1. Flavonoid/triterpene GT from M. truncatula .............................................. 0 8.2. Flavonoid specific glycosyltransferase (WsFGT) from W. somnifera ................................... 0 8.3. Flavonoid glucosyltransferase (CaUGT3) from C. roseus ......................................... 0 9. BiotechnologicalandbiomedicalapplicationsofGTs............................................. 0 9.1. Roleindefensemechanism..................................................... 0 9.2. Synthesisofvaluableglycoconjugates................................................ 0 9.3. GTsinvolvedinhormonalregulation................................................ 0 9.4. GTs involved in modification of xenobiotics and detoxificationofpollutants............................... 0 9.5. GTsinvolvedinsecondarymetabolitebiosynthesis.......................................... 0 9.6. Stabilizationofsecondarymetabolites................................................ 0 9.7. Plant-microbeinteractions..................................................... 0 9.8. Metabolicengineeringofcrops................................................... 0 9.9. PharmacologicalstudiesusingUGTs................................................. 0 10. Futureprospectsinglycosyltransferaseresearch.............................................. 0 Acknowledgments............................................................... 0 References.................................................................. 0 1. Introduction of a sugar moiety to low molecular weight secondary metabolites influ- ences acceptor's properties like solubility, stability, bioactivity, subcellu- Glycosyltransferases (GTs) catalyze stereospecific and regiospecific lar localization and binding properties with other molecules leading to transfer of nucleotide diphosphate-activated sugars to a wide and reduced toxicity of endogenous and exogenous substances (Lim et al., diverse range of molecules from proteins, lipids, nucleic acids to antibi- 2004). For example, terpenoids such as monoterpenols (geraniol and otics and other low molecular weight compounds known as secondary linalool) are toxic for the plant as such and are chemically hydrophic metabolites (Lairson et al., 2008; Weadge and Palcic, 2009). Glycosylation thus affecting their mobility and transport across tissues in plants. How- mechanism is the key modification step occurring in various biological ever, glycosylation results into the generation of a monoterpenol gluco- processes resulting in formation of myriad of plant secondary metabolites side which becomes transportable, less toxic, stable and also attains possessing glycodiversity. Together with hydroxylation, methylation and altered volatility affecting aroma (Bonishch et al., 2014). acylation reactions, glycosylation contributes to the complexity and di- Glycosyltransferases bear considerable importance and interest versity of plant secondary metabolites. As per the IUBMB guidelines, gly- owing to the fact that glycan moiety forms an integral and essential cosyltransferases have separate Enzyme Commission numbers and are component of natural products, conferring pharmacological properties classified on various parameters including similarities based on amino to the molecule leading to enhanced bioavailability, reduced toxicity acids (Campbell et al., 1997; Coutinho et al., 2003), substrate specificity, and increased solubility. Although, the present trends have highlighted reaction mechanism (inversion or retention of anomeric carbon) the significant prospects of GTs in drug-designing and development, the (Coutinho et al., 2003), 3D structures (GT-A, GT-B or predicted GT-C) stringent specificity of some GTs limits glycodiversification and intro- and type of reaction. Till 2015, GTs have been classified into 97 families duces the need for GT engineering (Williams et al., 2007)whileothers (GT1-GT97, (http://www.cazy.org/GlycosylTransferases)withGT-1fam- are promiscuous tools in alterations involving glycosylation patterns. ily consisting of maximum candidates of UGT genes. 108 GT crystal struc- Emerging trends in glycoengineering have witnessed the manipulation tures are reported in Protein data bank comprising of 40 members of