Glycans are vital components of glycoproteins, glycolipids, and proteoglycans in all domains of life. Glycoproteins are grouped by the type of carbohydrate and amino acid linkage site. N-linked glycosylation is a modification of asparagine, whereas O-linked glycosylation occurs through the hydroxyl group of serine and threonine residues. Glycosylation occurs co- or post-translationally on >50% of eukaryotic proteins resulting in membrane-associated, intracellular, or secreted glycoproteins that are crucial in cellular processes, protein bioactivity and metabolic turnover. Modification by O-linked-N-acetyl glucosamine (O-GlcNAc) has rapidly emerged as a major cellular signaling mechanism with number of modified targets similar to protein phosphorylation. Many oncogenes and tumor suppressors are regulated by O-GlcNAcylation. O-GlcNAc modification is ubiquitous among eukaryotes, from yeast to humans and its modifying enzymes have been well characterized. O-GlcNAc modified nuclear and cyto