A-Acetylglucosamine residues

The structure of chitin is rather similar to that of cellulose, though it is composed of P1 -> 4-linked A -acetylglucosamine residues. Chitin is a major constituent in insect skeletons and the shells... 

This enzyme [EC 3.2.1.50] catalyzes hydrolysis of terminal nonreducing A-acetylglucosamine residues in N-ace-tyl-a-glucosaminides. 

Carbohydrates are linked to some soluble proteins as well as membrane proteins. In particular, many of the proteins secreted from cells are glycosylated. Most proteins present in the serum component of blood are glycoproteins (Figure 11.20). Furthermore, A-acetylglucosamine residues are O-linked to some intracellular proteins. The role of these carbohydrates, which are dynamically added and removed, is under active investigation. 

In contrast to sero- and lactotransferrins, glycans of ovotransferrins from avian egg-white contain a bisecting A-acetylglucosamine residue, like other glycoproteins from oviducts, such as ovomucoid and ovalbumin for instance (Fig. 16A-C). Like all of the avian egg glycoproteins, ovotransferrins are not fueosylated. 

Rat mammary-gland transferrin. Rat milk transferrin contains four glycovari-ants that differ only in their sialic acid content. The primary structure of the two major variants has been determined by Escriva et al. [67]. As shown in Fig. 8D, the glycoforms contain either one or two A-acetylneuraminic acid residues a-2,6-linked to galactose in a conventional diantennary glycan of the A-acetyllactosaminic type. Most contain fucose a-l,6-linked to the proximal A-acetylglucosamine residue. 

A fundamental finding revealed that the high affinity binding of N-linked glycopeptides to the pea (and lentil) lectins requires the presence of an a-L-fucosyl residue attached to the asparagine-linked A-acetylglucosamine residue [90,95]. 

Fig. 4 Schematic representation of polysaccharide intercellular adhesin (PIA). The backbone of the unbranched polysaccharide consists of (3-1,6-linked A-acetylglucosamine residues. PI A carries 15% non-A-acetylated, free 2-amino groups and O-succinoyl ester residues. The presence of negative and positive charges is apparently of functional relevance for intercellular adhesive properties of PIA...

Fig. 17.4 Simplified structure of a complex N-linked glycan and the sites of action of B-hexosaminidase. Glycoproteins are degraded by specific enzymes from both directions. Lysosomal catabolism is terminated when an A-acetylglucosamine residue is encountered by the catalytically impaired enzyme B-hexosaminidase, and thus the glycoprotein-derived oligosaccharide in the box accumulates in Sandhoff patients.

The A-acetylglucosamine residues of the glycan chains are a strikingly immutable feature of peptidoglycans. The only room for variation appears to be in whether or not they all contain A-acetyl groups. 

Ogawa, R., Miura, Y., Tokura, S., and Koriyama, T. 1992. Suseeptibihties of bacterial cellulose eontain-ing A-acetylglucosamine residues for cellulolytie and ehitinolytie enzymes. International Journal of... 

Shirai, A., Sakairi, N., Nishi, N., and Tokura, S. 1997. Preparation of a novel (1 —> 4)- 3-D-glycan hy Acetobacter xylinum—A proposed mechanism for incorporation of a A-acetylglucosamine residue into bacterial cellulose. Carbohydrate Polymers 32(3-4) 223-227. 

TttETiBR, V. Altmann, R MArz, L. Peptide-A4-(A-acetyl-glucosaminyl)asparagine amidase F cannot release glycans with fucose attached a-(l—>3) to the asparagine-linked A-acetylglucosamine residue. Eur. 

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