User:Kinkreet/Glycoproteins

Glycoproteins are macromolecules composed of a protein and a carbohydrate or oligosaccharide. Additions of sugars can occur at asparagine sites and are called N-Glycosylation or at serine or threonine and are called O-Glycosylation. A Monosaccharide that is common in glycoproteins is glucose. While these proteins are common in nature, they are relatively rare in bacteria. They occur in cells and show a phenomenon called “microheterogeneity” meaning that a variety of structurally different carbohydrate units can be found at even a single attachment site. Ovalbumin contains one glycosylated amino acid but over a dozen different oligosaccharides. Soluble glycoproteins show a high viscosity such as seen in egg whites. Sugar groups assist in protein folding (usually found in the Endoplasmic reticulum) and improve the stability of the glycoprotein. Glycoproteins are essential to the immune system, especially in mammals. Some glycoproteins are present in blood group antigens, hormones (such as Thyroid Stimulating Hormone) and Erythropoietin (EPO) a major component to red cell production. The absences of glycoproteins can lead to major diseases classified as “Glycogen Storage Diseases” which encompass over 40 diseases such as Mannosidosis, Mucolipidosis and Sialidosis. Specific glycoproteins have been identified in many diseases. Some mucin glycoproteins are associated with asthma and lung health, some with Cystic Fibrosis and others are linked to colon and bowel disorders. Glycoproteins are associated with muscular and neurodegenerative disorders, such as Alzheimer’s and Muscular Dystrophy. Viruses, bacteria and parasites take advantage of cell surface carbohydrates associated with glycoproteins, using them to gain access to enter a cell. For example, rhinoviruses use I-Cam to gain entry, while parvovirus B19 uses an erythrocyte specific antigen (P antigen) to infect red cells. Helicobacter Pylori uses a Lewis blood group antigen on the surface of gastric mucinous cells to gain access. Glycoproteins play an integral part in both our health and well being and in the discovery of disease states and how those diseases will be treated. Glycoproteins and their carbohydrate links are being investigated as drug delivery systems to treat and cure disease.