Hyaluronic acid hexosamine

Disaccharides of the hexuronic acid-hexosamine type constitute the fundamental repeating unit of many mucopolysaccharides, from which they are derived by hydrolytic degradation. Further hydrolytic treatment results generally in destruction of the uronic acid moiety of the disaccharide. Structural studies have been made on the disaccharides from hyaluronic acid (hyalobiouronic acid), chondroitinsulfate (chondrosine), and heparin (heparosine). 

These materials are also called aminopolysaccharides by Kent (K15, K16) or mucopolyuronides by Blix (B22). They contain uronic (hexu-ronic) acid, usually n-glucuronic acid. Only one other uronic acid occurring together with n-glucuronic acid, namely t-iduronic acid, has been found in chondroitin sulfate B (dermatan). In addition to uronic acid, most of these materials, with the exception of hyaluronic acid, contain sulfates (in ester form). They also contain hexosamine as glucosamine or galactosamine, frequently in acetylated form. 

As early as 1964 and in later publications, it was possible to demonstrate the significance of glycoproteins (hexosamine, fucose, sialic acid [34], etc.) and cholinesterase for the detection of non-inflammatory, inflammatory or malignant disease and their follow-up as well as for the distinction between transudate and exudate in a so-called phlogogram (E. Kuntz, 1964). (see footnote p.298) Because of the significance and pathophysiological features of the mucopolysaccharides, appropriate biochemical parameters are likely to be of further interest. In addition, elevated values of hyaluronic acid have been found in the ascitic fluid of cirrhotic patients. 

These proteins are composed of simple proteins in combination with carbohydrates like mucopolysaccharides, which include hyaluronic acid and chondroitin sulphates. On hydrolysis, mucopolysaccharides yield more than 4% of amino-sugars, hexosamine and uronic acid e.g., ovomucoid from egg white. Soluble mucoproteins are neither readily denatured by heat nor easily precipitated by common protein precipitants like trichloroacetic acid or picric acid. The term glycoproteins is restricted to those proteins that contain small amounts of carbohydrate usually less than 4% hexosamine. 

Stacey has written an excellent review on the subject of mucopolysaccharides, which he classified on the basis of their containing both hexosamine and hexuronic acid residues, one or the other of these sugar derivatives, or neither. Hyaluronic acid, chondroitinsulfuric acid. Type I pneumococcal polysaccharides, and heparin are members of the first class. Types II, III, and VIII pneumococcal polysaccharides are examples containing hexuronic acid but no hexosamine. Chi tin and Types IV and XIV pneiuno-coccal polysaccharides contain hexosamine but no hexuronic acid and bacterial dextrans, mold polysaccharides, and levans contain neither hexosamine nor hexuronic acid. 

B. Heterozooglycans (heterozoopolysaccharides). Zoopolysaccharides which contain two or more types of monosaccharide, hexosamine, or uronic acid. (Examples Hyaluronic acid, chondroitin sulfate, heparin, blood-type polysaccharides, keratosulfate.)... 

The proteoglycans contain heteropolysaccharides known as glycosaminoglycans, an unwieldy term that emphasizes their content of hexosamines and uronic acids. Formerly glycosaminoglycans were known as mucopolysaccharides. The best known members of this group are the chondroitin sulphates and hyaluronic acid. Though they are characterized by the structure of their polysaccharide chains, these are almost invariably associated with protein, hence the term proteoglycan. 

Hexosamine is found as the 2-amino derivative of glucose or galactose in a wide variety of polysaccharides such as chitin, hyaluronic acid, and many others. Very little is known of its origin or path of degradation. ... 

L-Glutamine donates nitrogen for hexosamine synthesis in Neurospora crassa and for the n-glucosamine units of hyaluronate in streptococci. Of twenty-three amino acids (and ammonium chloride) tested with group A streptococci, L-glutamine was the only consistent nitrogen-donor for... 

The place of L-glutamine in hyaluronate synthesis is shown by experiments with methionine sulfoxide. Since methionine sulfoxide (2-amino-4-methylsulfinylbutyric acid) inhibits L-glutamine formation the addition of the sulfoxide to a culture of hemolytic streptococci inhibits hexosamine synthesis and, consequently, hyaluronate formation. This inhibition can take place at concentrations of methionine sulfoxide which are low enough not to inhibit hyaluronate synthesis with L-glutamine. ... 

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