Classification of glycoproteins

Classification of glycoproteins
Glycoproteins result from the covalent association of carbohydrate moieties with protein. The amino acids and carbohydrates comprising the glycoprotein molecules are organised in two general ways. One type has a protein core, frequently molecular weight less than 100,000 to which are attached a few oligosaccharides residues.

The other type has a much higher molecular weight and is mainly cabohdydrate in content and is organised as hundreds of small oligosaccharides residues covalently linked to a peptide core.

Classifications of glycoproteins is based in the type of glycosidic linkage involved in the attachment of carbohydrate to the peptide backbone.
*Glycoproteins having one carbohydrate group in each protein group
Ovalbumin MW 44.5x1000
Soybean hemagglutinin MW 110x1000
Ceruloplasmin MW 143x1000
Transferrin MW 92x1000

*Glycoproteins having a few carbohydrates groups in each protein unit
Ovomucoid MW 28x1000
Fibrinogen MW 330x1000
Fetuin MW 46x1000
D-glucose oxidase MW 186x1000
Thyroglobulin MW 600x1000

*Glycoproteins having many carbohydrate groups in each protein unit
Epithelial mucins MW 1000x1000
Blood group substance A MW 416x1000
Classification of glycoproteins

What is glycoprotein?

Glycoproteins may be defined as biopolymers having amino acids and sugar reduces link covalently to each other. They are widely distributed in nature. Found in higher animals, plants and microorganisms, glycoproteins contain a protein chain of any of the 20 naturally occurring L- α -amino acid units.

Proteoglycans are a subclass of glycoproteins with distinctive structure. Glycoproteins differ from monosaccharides protein structures in that they contain considerably less carbohydrate.

The mucopolysaccharides however may be considered a type of glycoprotein. Formed in the Golgi apparatus in the process of glycosylation, glycoproteins are important components of plasma membranes in which they extend throughout the lipid layer.

The molecular weights of glycoprotein range from 15,000 up to million. Some glycoproteins have only one glycochain in a molecule, whereas other glycoprotein possesses many glycochains in a molecule. The carbohydrate chains of glycoproteins are short, consisting perhaps eighth to ten saccharides units.

D-galactose, N-acetyl-D-galactosamine, D-glucose,  N-acetyl-D-glucosamine, D-mannose, L-fucose, and sialic acid, comprise the bulk of the carbohydrate moiety.
What is glycoprotein?