Glycans
From Wikipedia, the free encyclopedia
Glycans are polysaccharides. Usually, this word is used to refer to the carbohydrate moiety of a glycoprotein. There are two types: O-linked and N-linked. O-glycans consist of N-acetyl galactosamine, galactose, and neuraminic acid. N-glycans consist of N-acetylglucosamine, fructose, mannose, galactose, and neuraminic acid. N-glycans are derived from a 14-sugar unit consisting of 14 residues (3 glucose, 9 mannose, and 2 N-acetylglucosamine). O-glycans, on the other hand, have one sugar added at a time. Examples of O-linked glycoproteins are:
- Glycophorin, a protein in erythrocyte cell membranes
- Mucin, a protein in saliva involved in formation of dental plaque
- Notch, a transmembrane receptor involved in development and cell fate decisions
- Thrombospondin
- Factor VII
- Factor IX
- Urinary type Plasminogen Activator
Most glycoproteins are N-linked and have 5-15 sugar residues. O-linked glycoproteins have 1-4 sugar residues.