Uronic sugar acids

HemiceUulose is a mixture of amorphous branched-chain polysaccharides consisting of a few hundred sugar residues. They are easily hydrolyzed to monomeric sugars and uronic and acetic acids. Many different hemiceUuloses have been isolated from wood. 

Class Amino sugar" (usually as acetamido (W-acetyl) derivative Uronic acid Uronate Ulosonic acid Ulosonate The sialic acid family ... 

ChSS was fractionated on a column (550 x 15 mm) of DEAE Sepharo e Fast Flow using a Hiload System (Pharmacia), which was initially equilibrated in 0.005 M NaAc-bufFer pH 5.0. The sample was dissolved in water, the insoluble residue was removed by centrifugation and the supernatant was applied onto the column. After applying the gradient shown in Figure 1, the residual polysaccharides were washed from the column using 0.5 M NaOH. Fractions (23 ml) were collected and assayed by automated methods [2,3] for total neutral sugars and uronic acids. 

Rha, Ara and Gal are the neutral sugar components from all the fractions. Xyl is not present in Fla and is significantly present in the hemicellulose fractions, indicating that this monosaccharide is component of hemicellulosic polymers. Chemical composition of the water fractions were determined (Table V). High protein contents and the presence of O-acetyl-groups were observed in four aqueous fractions. Neutral sugar and uronic acid composition points to inclusion of these polymers in the class of pectic polysaccharides. 

Reduction of uronic acids Uronic acids (UA) were converted to the corresponding neutral sugars (NS) by carbodiimide activation of the carboxyl groups followed by a reduction with NaBD4 according to the method of Kim and Carpita [5]. In order to achieve a complete reduction of the uronic acids the procedure was repeated once. 

The purification of a pneumococcal polysaccharide may be difficult, and the polysaccharide material is sometimes contaminated by a cell-wall component known as the C-substance. The methods for structural analysis of polysaccharides (which, like several of the pneumococcal polysaccharides, contain amino sugar and uronic acid... 

There are three possible classes of sugar acids which may be produced by the oxidation of monosaccharides (Figure 9.11). The aldonic acids are produced from aldoses when the aldehyde group at carbon 1 is oxidised to a carboxylic acid. If, however, the aldehyde group remains intact and only a primary alcohol group (usually at carbon 6 in the case of hexoses) is oxidised then a uronic acid is formed. Both aldonic and uronic acids occur in nature as intermediates in... 

Synthesis of GAGs requires the sequential attachment of an jV-acetyl amino sugar or uronic acid to the protein core molecule (Figure 9.2), each step being catalysed by a... 

C. Raba. and K. Fischer, Ion-Pair HPLC Determination of Sugars, Amino Sugars, and Uronic Acids, Anal- Chem. 2001,... 

All fractions should have their combined neutral sugars and uronic acid (and cellulose if appropriate) contents checked against the weight of the fraction. Except for the initial fractions, which contain protein and other cellular components, the combined carbohydrate analyses figures should agree approximately with the weight of the fraction. 

Three kinds of sugar acids can be formally obtained from the corresponding aldoses. They are aldonic acids, produced by oxidation at C-l of the aldose uronic acids, formed by oxidation of the primary alcohol group of the aldose and aldaric acids, formed by oxidation of both the aldehyde and the primary alcohol group. 

Mopper, K. (1977) Sugars and uronic acids in sediment and water from the Black Sea and North Sea with emphasis on analytical techniques. Mar. Chem. 5, 585-603. 

Sugar acids, mono-, di-, and tri-carboxylic acids, keto-, hydroxy-acids as well as unsaturated organic acids are present in foods. While uronic acids participate in the browning reaction, others might accelerate or retard the reaction. 

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