Using our distinguished High-Affi™ technology, Creative Biolabs can produce customized anti-glycosylated polyclonal or monoclonal antibodies against five classes of glycans including N-linked glycosylation, O-linked glycosylation, phospho-serine glycosylation, C-mannosylation, and the formation of GPI anchors (glypiation), which tremendously diversifies the application field of glycosylation-specific antibody.
Glycosylation is admitted to the most complex and diverse post-translational modification by which a mono- or oligo-saccharide is covalently attached to a target macromolecule, such as proteins and lipids. The process of glycosylation is an enzyme-directed site-specific process as opposed to the non-enzymatic chemical reaction of glycation. The enzymes glycosyltransferases and glycosidases are responsible for this process. Glycosylation produces an abundant, diverse, and highly regulated repertoire of cellular glycans that are frequently attached to proteins.
Base on the types of modified amino acids and characteristic of sugar chains, glycosylation can be divided into the following five categories:
1) N-linked glycosylation
N-linked glycosylation is an attachment of an oligosaccharide molecule to an amide nitrogen atom of asparagine (Asn) or arginine (Arg) of proteins. The N-linked glycosylation process is highly conservative and occurs in all kinds of lives. The types of N-linked glycans attached to a glycoprotein differ in species and vary across proteins and cells wherein the N-linked glycans are expressed. Three steps summarize the biosynthesis of N-linked glycans, first with the synthesis of dolichol-linked precursor oligosaccharide, and then En bloc transfer of precursor oligosaccharide to protein, at last processing of the oligosaccharide. N-linked glycoproteins distribute on any parts of the cell and play an important role in protein stability and solubility, cell migration, cell-cell and cell-matrix interactions, and cellular signaling transduction. Abnormal expression and structural changes result in a variety of diseases, most of which involve the nervous system disorders, cancer, and autoimmune diseases.
2) O-linked glycosylation
O-linked glycosylation is an attachment of a monosaccharide or an oligosaccharide molecule to an oxygen atom in an amino acid residue of proteins. The process of O-linked glycosylation occurs in the Golgi apparatus in eukaryotes, and may also be found in archaea and bacteria. This starts with the addition of N-acetyl-galactosamine, fucose, glucose or mannose to serine or threonine residues transferred by the corresponding glycosyltransferases; then the carbohydrate chains extend followed by other carbohydrates (such as galactose and sialic acid). Interestingly, an O-linked glycosylation by monosaccharide [N-acetyl-galactosamine (O-GalNAc) or O-N-acetylglucosamine (O-GlcNAc)] may occur on serines or threonines in proteins. In signaling pathways, it can co-regulate with phosphorylation. O-glycosylation abnormalities have been found in autoimmune diseases and neurodegenerative diseases, especially in cancer. Aberrant O-glycosylation structure is observed in diverse types of cancer, i.e., the formation of Tn, sialyl-Tn structures, and hyperGlcNAcylation. These aberrant glycoproteins are recognized by antibodies.
3) Phospho-serine glycosylation
Phospho-serine glycosylation is an attachment of sugar to proteins via a phosphodiester bond. GlcNAc, xylose, mannose and fucose have been found involved in this kind of glycosylation. GlcNAc and fucose have been found in varieties of proteins in Dictyostelium discoideum. Mannose is observed in Leishmania mexicana, and xylose is reported in Trypanosoma cruzi.
C-mannosylation refers to adding a mannose sugar to the first tryptophan residue C-2 in the sequence W-X-X-W (W indicates tryptophan; X is any amino acid) through C-C bond. This linkage has been so far found in mammalian proteins including RNase2, thrombospondins, interleukin-12 and properdin.
5) Glypiation (GPI)
Glypiation (GPI) is a special form of glycosylation that protein is attached to a lipid anchor via a glycan chain. This kind of glycosylation is widely distributed among important cell surface glycoproteins, including trypanosomes and Thy-1 antigen.
Fig. 1 Diagrammatic representation of the five distinct types of sugar-peptide bonds. (Spiro 2002)
Fig. 2 Initiation and maturation of the major types of eukaryotic glycoconjugates. (Varki et al. 2009)
As glycosylation modification usually acts on the characteristic and disease state-specific marker, glycosylation antibodies have been exploited gradually as detection tools or diagnostic reagents. The high-quality antibodies against different types of glycosylation produced by Creative Biolabs via High-Affi™ technology are surely applicable in these fields to meet our clients’ specific requirements.
In addition to the glycosylation-specific antibody, Creative Biolabs also provides a comprehensive list of PTM-specific antibody production services of your choice.