Hexosamine

Glycoproteins or mucoproieins. Compounds of proteins with carbohydrates. All glycoproteins contain a hexosamine and usually sulphate, ethanoate and glucuronic acid. The carbohydrate-protein linkages are, in some cases covalent and in others of the salt type. Aqueous solutions of glycoproteins are extremely viscous. [Pg.332]

Properties and Structure. a -Acid glycoprotein (a -AGP) has a molecular mass of about 41,000 and consists of a peptide chain having 181 amino acid residues and five carbohydrate units (14,15). Two cystine disulfide cross-linkages connect residues 5 and 147 and residues 72 and 164. The carbohydrate units comprise 45% of the molecule and contain siaUc acid, hexosamine, and neutral hexoses. In phosphate buffer the isoelectric point of the... [Pg.98]

Amino Sugars (Hexosamines) Are Components of Glycoproteins, Gangliosides, Glycosaminoglycans... [Pg.106]

Acetyl hexosamines N-Acetylglucosamine (GIcNAc) N-Acetylgalactosamine (GalNAc)... [Pg.109]

IonPac KC-811 column separated the labile compounds N-acetylneuraminic acid and N-glycolylneuraminic acid released by mild acid hydrolysis of bovine vitronectin.245 Sialic acid is extremely labile to conditions of handling and must be released by mild acid hydrolysis.246 Derivatization with phe-nylisothiocyanate and separation by reversed phase chromatography was found useful in analysis of hexosamines from gastric mucosa.247 A review on separation of sugars and other carbohydrates which covers many important aspects is available.248... [Pg.252]

Ishihara, K., Kameyama, J. -I., and Hotta, K., Development of an HPLC method to estimate hexosamines and its application to determine mucin content in rat and human gastric mucosa, Comp. Biochem. Physiol., 104B, 781, 1993. [Pg.282]

Name Abbreviation Major uronic acidfe and hexosamine Main repeating disaccharides... [Pg.55]

Although widely used, colorimetric methods for determining total ur-onic acid and hexosamine are now regarded as providing, at best, only semi-quantitative estimates of heparin.42 Colorimetric reactions in a strong acid, such as the carbazole reaction for the uronic acids48 and the Morgan-Elson reaction for the hexosamines,49 are not specific for hepa-... [Pg.61]

Conclusive evidence for the a-L configuration of the idosyluronic-to-hexosamine bond was provided by 1H-n.m.r. studies on disaccharide 7, obtained as the major product ( 75% yield) of the cleavage of heparin by heparinase.106 This configuration is consistent also with the 1H- and 13C-n.m.r. spectra of disaccharide 6 (the major product from nitrous acid cleavage of heparin103-106) and of unmodified heparin.82-84... [Pg.70]

Both positional linkages (uronic acid to hexosamine and hexosamine to uronic acid) were established as being (1 — 4) by structural analysis of the previously mentioned (see Section IV), crystalline disaccharides containing D-glucuronic acid, isolated from an acid hydrolyzate of carboxyl-reduced heparin.128-129 Further evidence was obtained from the structure of the D-glucuronic acid-containing counterpart of disaccharides 6 and 8, obtained as minor products from pig-mucosal heparin following nitrous acid deamination,1110 136-138 and acid hydrolysis followed by N-acetylation,130 respectively. [Pg.72]

The amino sugar counterparts of D-glucuronic acid and nonsulfated L-iduronic acid in heparin are either N-acetylated, or nonsulfated at C-6, or both. 2-Acetamido-2-deoxy-D-glucosyl residues account for only a minor proportion of the total hexosamine in heparin, and are especially low in beef-lung preparations (see Table II).8,138,147 -149 In contrast, they... [Pg.73]

Although the glycosidic bonds of uronic acid residues are usually more resistant to acid hydrolysis than those of neutral polysaccharides,218 these linkages in heparin are more readily cleavable then those between the hexosamine and the uronic acid residues. Disaccharides obtained by exhaustive hydrolysis of heparin with 0.5 MHC1 at 80° contained hexu-... [Pg.84]

A computer-built model, having an axial rise per disaccharide of 0.84 nm and possible stabilization by an 0-3-H 0-5, intramolecular hydrogen-bond from a hexosamine to a uronic acid residue, is a rather extended, two-fold helix (see Fig. 8),346 with each fold approximately corresponding341,346 to the disaccharide repeat in Fig. 7a. A substantially similar model was obtained by use of calculations also taking into consid-... [Pg.109]

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