GLYCOSAMINOGLYCAN

'Glycosaminoglycans' (GAGs) or 'mucopolysaccharides' are long unbranched polysaccharides consisting of a repeating disaccharide unit.

Contents

Production

Structure

Function

Classification

See also

External links

Production

They are synthesized in either the endoplasmic reticulum or Golgi apparatus.

Structure

This unit consists of an N-acetyl-hexosamine and a hexose or hexuronic acid, either or both of which may be sulfated.
The combination of the sulfate group and the carboxylate groups of the uronic acid residues gives them a very high density of negative charge.

Function

This family of carbohydrates is essential or important for the life of vertebrates and an assortment of lower animals.
GAGs form an important component of connective tissues. GAG chains may be covalently linked to a protein to form proteoglycans.

Classification

Members of the glycosaminoglycan family vary in the type of hexosamine, hexose or hexuronic acid unit they contain (e.g. glucuronic acid, iduronic acid, galactose, galactosamine, glucosamine).
They also vary in the geometry of the glycosidic linkage.
Examples of GAGs include:

'Name'	'Sugar 1'	'Sugar 2'	'Linkage'	'Unique features'
Chondroitin sulphate	N-Acetylgalactosamine	glucuronic acid	beta (1,3)	Most prevalent GAG
Dermatan sulphate	iduronic acid	N-Acetylgalactosamine	beta (1,3)	Only one with iduronic acid
Keratan sulphate	galactose	(varies)	beta (1,4)	Very variable
Heparin	glucuronic acid	glucosamine	alpha (1,4)	Only one intracellular; high negative charge density
Heparan sulphate	glucuronic acid	glucosamine	alpha (1,4)	Similar to heparin but extracellular
Hyaluronan	glucuronic acid	N-Acetylglucosamine	beta (1,3)	Only bacterial one, only one without sulfur

See also

★ Mucopolysaccharidosis (lysosomal storage diseases)

★ Lipopolysaccharide

External links

★ Proteoglycans and Glycosaminoglycans at Lancaster University

★ Illustration at scientificpsychic.com

★ King M. 2005. Glycosaminoglycans. Indiana University School of Medicine Accessed December 31, 2006.

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