Glycobiology: The technologies associated with glycoprotein analysis

Protein glycosylation is ubiquitous being found on molecules in both eukaryotes and to an increasing extent prokaryotes. Why are proteins modified with sugars? One general consequence for glycosylation on proteins is that the glycosylation imparts proteinase resistance. There are numerous examples of glycoprotein instability following the site directed metagenesis of a glycosylation site on proteins such as the GLYT1 glucose transporter protein, Human transferrin receptor and the angiotensin-converting enzyme, all expressed in chinese hamster ovary cells. However, increasingly glycosylation on proteins has been found to be important for protein trafficking, biological activity, cell-cell and cell extracellular matrix interactions (Varki, 1993). The broad interest in the structure and function of glycoproteins has led to a relatively new discipline, glycobiology. The principal aim of glycobiology is to understand the structure and function of the carbohydrate attached to a variety of carriers including protein (glycoproteins, proteoglycans), lipid (lipopolysaccharides, glycolipids) and to protein and lipid (glycophosphatidyl inositol protein anchors, lipopeptidophosphoglycans). Understanding glycosylation patterns is also of relevance to recombinant protein design where it is desirable to engineer glycoproteins with a variety of physio-chemical properties including proteolytic stability, thermostability, elasto-viscosity and structural modulation of receptors (Dwek et al. 1993).