Glycoconjugates acid hydrolysis

Mild acid hydrolysis is less specific than sialidase digestion and also less expensive. Attention should be paid to the different conditions of hydrolysis required for various glycoconjugates and the slower release of 0-acylated sialic acids relative to Neu5Ac (Ledeen and Yu 1976) (see chapter C). To obtain optimal quantitation, a release curve for sialic acid should be prepared (Schauer et al 1975, O Kennedy 1979). In addition to this precaution, the destruction of sialic acid under the conditions of the hydrolysis should be assessed (e.g. Schauer et al 1975, O Kennedy 1979). The inclusion of a sialic acid standard under the conditions of hydrolysis will allow assessment of the level of destruction (Schauer et al 1975, Schauer 1978, Caimi et al 1979). 

Because of the numerous methods available for the hydrolysis of various glycoconjugates, including glycoproteins, mucins, glycosaminogly-cans, and gangliosides, it is useful to arrange these methods according to the type of acid employed. Some studies compared a particular method of... 

Honda and coworkers used 4 M hydrochloric acid for 6 h at 100° for the hydrolysis of nondialyzable glycoconjugates when determining amino monosaccharides, but preferred 2 M CF3CO2H for 6 h at 100° when determining the neutral monosaccharides and uronic acids, as these compounds are subject to more-severe degradation by 4 M hydrochloric acid. They obtained complete hydrolysis (with >90% recovery of monosaccharides added prior to hydrolysis) by using these two sets of hydrolytic conditions. 

Sialidase or NA is the second glycoprotein on the virion surface. One of the most important functions of sialidase is associated with the release of virus progeny from infected host cells to repeat the cycle of infection [6, 50], The enzyme catalyzes the hydrolysis of sialic acid residues from glycoconjugates on the cell surface with either Neu5Ac(a2 3)Gal or Neu5Ac(a2 6)Gal linkages (Gal=galactose) [60, 61]. 

The NA (EC 3.2.1.18) catdyses the hydrolysis of the a-(2,3) and a-(2,6) glycosidic linkage between a terminal sialic acid and its adjacent carbohydrate moiety on a variety of glycoconjugates. 

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