GlcNAc residues

The first heteropolysaccharide for which a cyclic structure has been proposed is the enterobacterial common antigen (ECA), which was shown by f.a.b.-m.s. to be a mixture of three cyclic components containing 4, 5, and 6 repeats, respectively, of a previously characterized trisaccharide (31) in which the GlcNAc residues were known to be partially acetylated at 0-6. 

C5-1 antibody was produced in alfalfa, the glycan component consisted predominantly of a mature oligosaccharide comprising a core a(l,3)-fucose residue, a bisecting P(l,2)-xylose residue and two terminal GlcNAc residues (Fig. 15.4) [6],... 

The crystal structure of a pentamer of GlcNAc residues, representing the chitin polymer (poly-/l-(l-4)-GlcNAc), boimd to the chitinase enzyme ChiB from Serratia marcescens, revealed a narrow, timnel-like active site in the center of the TIM barrel fold [167]. Several conserved residues near the center of the site, which are important in catalysis, interact with the substrate via hydrogen bonds, while interactions farther from the center depend on van der Waals interactions. The sugar in the - 1 subsite adopts a boat conformation, presumably due to interactions with these critical active-site residues. 

Finally, the CG and CD atoms of the arginine residue of the tail occupy the positions of C3 and C4 of the + 1 GlcNAc residue. Thus, this arrangement may be considered structural mimicry, and one side of the - 1 sugar residue as well as part of the + 1 sugar residue are mimicked effectively by the peptide. 

The middle GlcNAc residues have a lower potential energy than the terminal residues for all curves in Figure la. Indeed sites C and D have the lowest energies of the hexasaccharide. This aspect contrasts with the poor steric contacts expected in site D if there were strain in the ring bound at this site (2 .). ... 

Table I. Energy of GlcNAc Residues in the Lysozyme-Substrate...

A heptasaccharide-lipid having 5 Man and 2 GlcNAc residues appears to be labelled rather quickly in Chinese-hamster ovary-cells,... 

---