Proteoglycans of intervertebral disc

Case contributed by Dr Francesco Sciacca

Schematic drawing of the proteoglycans of intervertebral disc.

Case Discussion

The proteoglycans are macromolecules; they are found in extracellular matrix.

Proteoglycans consisting of a protein nucleus to which side of glycosaminoglycans (GAGs) are bound: chondroitin-sulfate (CS) and keratan sulfate (KS) (ratio 2:1). The most important characteristic of GAGs is to be polyanionic molecules (they have many negative charges); therefore, they bind many water molecules. The molecules of CS are located near the carboxy-terminal portion of the protein nucleus (COOH); the KS molecules are located proximal to the bonding point of the CS. The amino-terminal portion (NH2) is, however, devoid of GAGs; presents to consider a specific one binding site for hyaluronic acid. Proteoglycans, in fact, can be found in the form of monomers or as large molecular aggregates, represented by monomers linked to a long chain of hyaluronic acid.

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