TISSUE BIOCHEMISTRY

Extracellular Matrix Components

Collagen Fibronectin Glycosaminoglycans Water Elastin

Glycosaminoglycan

Glycosaminoglycans are large complexes of negatively charged heteropolysaccharides chains

They have the ability to bind large amount of water .Thereby, producing the gel like matrix that form the basis of ECM.

They are generally associated with small amount of protein, forming proteoglycans ,which typically consist of 95% of carbohydrate.

Importance of glycosaminoglycans

The hydrated glycosaminoglycans serve as a flexible support for the ECM .

They interact with the structural and adhesive protein , and as a molecular sieve , influencing movement of material through the ECM.

The viscous , lubricating properties of mucous secretion also result from the presence of glycosaminoglycans , which led to the original naming of these compounds as mouco polysaccharides.

Role of glycosaminoglycans in formation of ECM

Glycosaminoglycans binds with water produces gel like matrix form the basis body ground substance which along with fibrous structrual proteins such as collagen and elastin , and adhesive proteins such as fibronectin , make up the extracellular matrix.

proteoglycan

All of the glycosaminoglycans , except hyaluronic acid are found covalently attached to protein , forming proteoglycan monomers.

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A proteoglycans monomer found in cartilage consist of a core protein to which the linear glycosaminoglycans chains are covalently attached.

These chains which may be composed of more than 100 monosaccharides, extend out from the core protein , and remain separated from each other because of charge repulsion.

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The resulting structure resembles a “BOTTLE BRUSH”

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In cartilage proteoglycan,the species of glycosaminoglycans include chondroitin sulfate and keratan sulfate

LINKAGE BETWEEN THE CARBOHYDRATE CHAIN AND THE PROTEINS

This linkage is most commonly through a trihexoside (galactose-galactose –xylose) and a serine residue, respectively an O-glycosidic bond is formed between the xylose and the hydroxyl group of the serine.

PROTEOGLYCAN AGGREGATE

The proteoglycan monomer associate with the molecule of hyaluronic acid to form proteoglycan aggregates. The association is not covalent but occur primarily through ionic interactions between the core protein and the hyaluronic acid.

The association is stabilized by additional small proteinhs called link proteins.