N-acetylgalactosamine residues

A number of enzyme have been reported to catalyze the hydrolysis of glycosidic linkages in glycoproteins at N-acetylgalactosamine residues, exhibiting specificities at either the a- or the /3-linkage. Enzymes that are reported to act on both a- and /3-linkages have to be clearly characterized as to their specificity. 

TABLE II. HUMAN NATURAL ANTIBODIES AGAINST GLYCOLIPIDS HAVING TERMINAL N-ACETYLGALACTOSAMINE RESIDUES... 

Figure 5 The structures of (1) glycosphingolipids and (2) the gangliosides G1V13 and Gmi contains ceramide, one glucose residue, one galactose residue, and one NANA residue. G i is a rno e complex ganglioside that contains an N-acetylgalactosamine residue and a galactose residue in addition to the components of Gm3.

Thus, the cell-wall polymer of Methanosarcina barkeri is reminiscent of chondroitin sulfate, a common component of the connective tissue in humans and animals. In contrast with chondroitin, it is not sulfated and contains two instead of one N-acetylgalactosamine residue in the repeating unit. Because of its similarities to chondroitin sulfate (Fig. 6), the shape-maintaining cell-wall polymer of Methanosarcina has been named methanochondroitin [60]. 

Although it was not proved unequivocally which specific hydroxyl groups were involved in the formation of the diborate inactive complex, it was concluded that the 3,4 hydroxyls of the galactose residues and the 4,6 hydroxyls of the N-acetylgalactosamine residues were the ones involved (Ahmed et al., 1976). Inspection of ball-and-stick... 

O-Linked Glycoproteins - The most common 0-linkage in glycoproteins involves a terminal N-acetylgalactosamine residue in the oligosaccharide linked to a serine or threonine residue of the protein (Figure 9.28). 

Roth, J., 1984, Cytochemical localization of terminal N-acetylgalactosamine residues in cellular compartments of intestinal goblet cells Implications of topology of O-glycosylation, J. Cell Biol. 98 399-406. 

Ando, S., Hirabayashi, Y, Kon, K., Inagaki, F., Tate, S., and Whittaker, V. P., 1992, A tri-sialoganglioside containing a sialyla2-6-N-acetylgalactosamine residue is a cholinergic-specific antigen, J. Biochem. 111 287-290. 

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