Hexosamine degradation

Depolymerization of the permethylated carbohydrate is achieved by hydrolysis with acid. Under these conditions, the amino sugar residues are N-deacetylated, and the aminohexosidic linkages become resistant to hydrolysis. Stellner and coworkers29 showed that, when the acid degradation is conducted in 95% acetic acid, the amino sugar residues are also liberated, and can be analyzed by the methylation technique.29 Therefore, acetolysis followed by acid hydrolysis is now commonly used, as it allows the analysis both of hexose and hexosamine residues. 

Dauwe, B., and J.J. Middleburg. 1998. Amino acids and hexosamines as indicators of organic matter degradation state in North Sea sediments. Limnology and Oceanography 43 782-798. 

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). 

Thus, the nonulosaminic acids were formulated as aldol condensation products of a hexosamine with pyruvic acid. This speculative concept received its first support with the isolation of A -acetyl-n-glucosamine as a degradation product of A -acetylneuraminic acid. These degradations employed nickel acetate plus pyridine or mild alkah for ten minutes. Besides A -acetyl-n-glucosamine and a number of unidentified degradation products, pyruvic acid was produced and was isolated as its (2,4-di-nitrophenyl) hydrazone. 

It appears that the main chemical structure of heparin as determined by degradation studies by the research groups of Wolfrom, Meyer and Stacey is an a-D-(l— 4) linked backbone structure of alternating hexosamine and uronic acid in which the hexosamine is 6-SO4, jV -S04-glucosamine and the uronic acid, 2- or 3-S04-glycuronic acid. The ratio of 2-5-2-6 rather than... 

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