Glycosidic bonds acid hydrolysis

Oligosaccharides result from the condensation of two to ten monosaccharide molecules through glycosidic bonds. Acid hydrolysis easily breaks these bonds enzymatic hydrolysis breaks them with high specificity. Saccharose (glucose + fructose) is the most abundant disaccharide. At present, most of the warm waxes for hair removal are prepared from saccharose (Tannir and Leshin, 2001). Maltose and cellobiose are degradation products of starch and cellulose polymers, respectively. 

Treatment of mushroom cultures with sodium [l- C]acetate and sodium [2- C]acetate yielded the two differently labell glycosides (28b). Acidic hydrolysis of the glycoside resulted in partial double bond migration, and two alygcones, (28a) and (30), were isolated. 

RNA is relatively resistant to the effects of dilute acid, but gentle treatment of DNA with 1 mM HCl leads to hydrolysis of purine glycosidic bonds and the loss of purine bases from the DNA. The glycosidic bonds between pyrimidine bases and 2 -deoxyribose are not affected, and, in this case, the polynucleotide s sugar-phosphate backbone remains intact. The purine-free polynucleotide product is called apurinic acid. 

The removal of the carbohydrate auxiliary group and the hydrolysis of the amino nitriles is achieved by acidolytic cleavage of the hemiaminal /V-glycosidic bond and the concomitant acid-catalyzed solvolysis of the nitrile using either hydrogen chloride in formic acid or hydrogen bromide in acetic acid56 57. 

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-... 

The reaction mechanism of a-amylases is referred to as retaining, which means that the stereochemistry at the cleaved bond of the carbohydrate is retained. Hydrolysis of the glycosidic bond is mediated by an acid hydrolysis mechanism, which is in turn mediated by Aspl97 and Glu233 in pig pancreatic amylase. These interactions have been identified from X-ray crystallography. The aspartate residue has been shown to form a covalent bond with the Cl position of the substrate in X-ray structure of a complex formed by a structurally related glucosyltransferase. " The glutamate residue is located in vicinity to the chloride ion and acts as the acidic catalyst in the reaction. The catalytic site of a-amylases is located in a V-shaped depression on the surface of the enzyme. 

---