Glycan Research
Glycans are compounds consisting of a large number of monosaccharides linked glycosidically. Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural, and physical roles in biological systems.
A Broad Classification of The Biological Roles of Glycans
There are several different ways to classify the biological roles of glycans, based on the glycan types in question, on the glycan-binding protein involved, etc. A simple and broad classification divides glycan functions into four somewhat distinct categories. The first is structural and modulatory roles. The second category involves extrinsic (interspecies) recognition. The third is intrinsic (intraspecies) recognition. Finally, there is molecular mimicry of host glycans. All of these categories can involve glycan-binding proteins.
Fig.1 General classification of the biological roles of glycans. (Varki, 2017)
Modifications of Glycans
It is well appreciated that the functions of nucleic acids and proteins are frequently modulated by chemical modifications of the main polymer. Carbohydrates and their modifications are extremely difficult to study. Like other biopolymers, the biological functions of carbohydrates can be modulated by modifying specific sites within an oligosaccharide/polysaccharide chain. Modifications can involve a variety of functional groups but most often entail the derivatization of hydroxyls or amino groups, such as acylation, sulfation, methylation, and phosphorylation.
Sulfated glycans are a major class of enzymatically modified glycans with important biological functions. All classes of glycans can be sulfated. Sulfated glycosaminoglycans (GAGs) are found on cell surfaces and within the extracellular matrix, where they mediate binding interactions and provide structural support. Sulfation similarly tunes the biological activity and physical properties of glycoproteins.
O-Acylation is a common, biologically important post-glycosylation modification of many glycans. O-acylation of glycans may include the transfer of a relatively small group like an acetyl group or a more complex structure, such as ferulate, to a sugar hydroxyl. Acylated glycans are found on cell surfaces, capsular polysaccharides of certain bacteria, and glycoconjugates. Acylation and de-acylation of glycans are catalyzed by acyltransferases and esterases, respectively. Changes in the acylation levels of glycans can significantly affect their specific molecular recognition events. More importantly, the acylation of glycans can play a role in human immunology, disease pathogenesis, and cancer progression.
Phosphorylation of carbohydrates is also an important feature in glycobiology. Phosphorylated glycans play key roles in protein transport, bacterial pathogenesis, and human diseases. Phosphorylation of carbohydrates occurs pre- or co-glycosylation.
O-Methylated carbohydrates have been found in various organisms and are most common in bacteria. In general, O-methylation occurs on mature glycans by O-methyltransferases that utilize S-adenosylmethionine (SAM) as the methyl donor. Detection and characterization of O-methylated glycans are achieved using various chemical and spectroscopic methods, including NMR and mass spectrometry.
While most modifications result in the decoration of oxygen or nitrogen atoms linked to monosaccharide residues, epimerization alters the stereochemistry at one of the carbon atoms producing a new monomer residue. One area where epimerization plays a key role is in the biosynthesis of certain glycosaminoglycans, including heparin, heparan sulfate, and dermatan sulfate.
Certain microorganisms are reported to produce enzymes that can carry out post-glycosylation modifications on host glycans.
Fig.2 Representative examples of common carbohydrate modifications in nature. (Muthana, 2012)
Glycan Related Research
Custom Services for Glycan Research
In addition to the customized services, we can also provide a variety of advanced technologies for glycan research, including but not limited to Lectin Microarray, MS, LC-ESI-MS, MALDI-TOF MS, GC-MS, HPLC, HPAEC-PAD, RP-HPLC, UHPLC/FLD/Q-TOF, FTIR, NMR, SPRi, TLC, Flow Cytometry.
As a comprehensive and leading biology company, Creative Biolabs has very senior experts in glycobiology research projects, and our technical staff have accumulated rich project experience. We use our advanced research and development expertise to help our customers solve difficulties and move projects forward. You can contact us to learn how we can serve your project through innovation, science, performance, and passion.
References
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Varki, A. Biological roles of glycans. Glycobiology. 2017, 27: 3-49.
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Muthana, S.M.; et al. Modifications of glycans: biological significance and therapeutic opportunities. ACS chemical biology. 2012, 7(1): 31-43.
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