Extracellular Matrix and Proteoglycans

1. TISSUE
BIOCHEMISTRY

2. Extracellular Matrix Components
 Collagen
 Fibronectin
 Glycosaminoglycans
 Water
 Elastin

3. 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.

4. 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.

5. 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.

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

7. Cont..
 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.

8. Cont..
 The resulting structure resembles a “BOTTLE BRUSH”

9. Cont..
 In cartilage proteoglycan,the species of
glycosaminoglycans include chondroitin sulfate and
keratan sulfate

10. 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.

11. 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.