Heteropolysaccharides uronic acids

Glycosaminoglycans are extracellular heteropolysaccharides in which one of the two monosaccharide units is a uronic acid and the... 

Heparin is a heteropolysaccharide whose chains consist of alternating derivatives of 2-amino-2-desoxy-D-glucose and uronic acid linked together via 1 - 4 glycoside bonds 12). 

The cell walls consist of highly sulfated heteropolysaccharide which consists of a complex mixture of neutral and amino sugars, uronic acids, glycine and an aminuronic acid (gulosaminuronic acid) (Table 4) [80-84]. The typical components of minein or pseudomurein are missing. 

Hemicellulose refers to a chemically ill-defined group of heteropolysaccharides of plant cell-walls that are closely associated with cellulose. They are composed of different hexoses and pentoses, and uronic acids. The hemicelluloses may be separated into two fractions, A and B however, there is no clear demarcation of structure between the two fractions. Hemicellulose B usually contains a higher proportion of uronic acid, chiefly 4-0-methyl-D-glucuronic acid, than the A fraction. The methyl ethers of D-aldobiouronic acids containing D-glucuronic acid, D-galacturonic acid, or D-mannuronic acid are isolated chiefly as the 4-O-methylaldobiouronic acids, and are hydrolyzed with difficulty by acid. 

In the case of glucose, the derivatives corresponding to these formulae are gluconic, glucaric and glucuronic acids, respectively. Of these compounds, the uronic acids, particularly those derived from glucose and galactose, are important components of a number of heteropolysaccharides. ... 

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. 

These are heteropolysaccharides composed of equal amounts of an amino sugar and a uronic acid, alternately linked through a glycosidic bond. Examples of mucopolysaccarides are chon-droitin sulphate, keratan sulphate and dermatan sulphate. They are consituents of connective tissue. Mucopolysaccarides are excreted in the urine in large amounts in the inborn errors of metabolism known as the mucopolysaccharidoses. 

In this study, we aimed at obtaining a heteropolysaccharide fraction in high yield by performing a hydrolytic pre-treatment step on wood chips followed by a room temperature extraction. Pre-treatment conditions involved acetic acid (AcOH), sulphur dioxide (SO2) and high temperature water. The isolated fractions were analysed for yield, chemical composition (sugars, uronic acids, and lignin) and molecular mass. 

Alteromonas macleodii svhsp.figiensis isolated from deep sea hydrothermal vent in North Fijian Basin is reported to produce EPS which is sul-fated heteropolysaccharide and has high uronic acids with pyruvate. The repeating unit of the EPS is a branched hexasaccharide containing glucose. 

Some heteropolysaccharides, not containing uronic acid residues, but containing three or more monosaccharide components, have been described, and their compositions are summarized in Table III. Most form aqueous solutions of a gummy or mucilaginous nature, and some are used commercially as hydrocolloids. 

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