Physico-Chemical and Functional Differences of Polysaccharides

As was mentioned, beta-D-glycans, to which hyaluronan is related, are extracellular or intercellular polysaccharides. It is important to find out what new HA and related glycosa-minoglycans have been introduced into the intercellular relations of chordate animals. To do that, let s look at the differences of the chemical structures and physico-chemical properties of polysaccharides with the purpose of understanding what physiological functions they perform. 

The beta-configuration of the 1-4-bonds in the cellulose molecule leads to extended polymer chains that form long and water-insoluble fibrils as a result of intermolecular hydrogen bonding. Further, while the alpha-l-4-bonds of glycogen and starch are hydrolysed with animal enzymes (alpha-amylases), the beta-l-4-bonds in the molecule of cellulose are not hydrolysed, since animals do not have the corresponding gene for cellulase, the enzyme that hydrolyses cellulose. 

The long parallel chains of chitin are arranged in tufts similar to those of the cellulose chains. Chitin is involved in the composition of cuticles, the external skeletons of invertebrate animals and cell envelops of fungus, where it is usually bound to proteins, lipids, pigments, inorganic salts and most typically, potassium carbonate [2], 

The main branches of the evolutionary species tree clearly differ in their polysaccharide composition. The most ancient structural polysaccharides are most likely murein-fotming cell walls of bacterial cells. The structural basis of murein comprises long parallel-oriented polysaccharide chains composed of N-acetyl-D-glucosamine and N-acetyl muiamic add linked by beta-1-4-bonds. The chains of polysaccharides are cross-linked by short polypeptide fragments of various compositions in different bacteria. 

3 Biochemical Features of Hyaluronic Acid and Other Glycosaminoglycans 

---