N-Acetylglucos-amine

Fig. 15.3 Plant and mammalian N-glycans have different structures. As illustrated here, a core structure (in gray) is common to plant and mammalian biantennary complex N-glycans. However, differences in the glycan processing machineries in plants and in mammals result in the absence of sialic acids in the terminal position of the antennae and the presence of a bisecting p (1,2) -xylose and of an a(l,3)-fucose residue in PMPs instead of the a(l,6)-fucose linked to the proximal N-acetylglucos-amine of native mammalian N-glycans.

M Crouvoisier, D Mengin-Lecreulx, J van Heijenoort. UDP-N-acetylglucosamine N-acetylmuramoyl-(pentapeptide) pyrophosphoryl undecaprenol N-acetylglucos-amine transferase from Escherichia coli. overproduction, solubilization, and purification. FEBS Lett 449 289-292, 1999. 

Brown K, Pompeo E, Dixon S, Mengin-Lecreulx D, Cambillau C, Bourne Y. Crystal structure of the bifrmctional N-acetylglucos-amine 1-phosphate uridyltransferase from Escherichia coli a paradigm for the related pyrophosphorylase superfamily. EMBO J. 1999 18 4096-4107. 

Hinderlich, S. Berger, M. Schwarzkopf, M. Effertz, K. Reutter, W. Molecular cloning and characterization of murine and human N-acetylglucos-amine kinase. Eur. J. Biochem., 267, 3301-3308 (2000)... 

Plant estrogens and metabolites of these compounds that have been excreted by animals have been fractionated on dextran gel columns (Nilsson, 1962). Gel filtration has been used in an investigation of polyphenols from brewery wort (Woof, 1962). The catecholamines adrenalin and noradrenalin can be separated from plasma proteins on Sephadex (Marshall, 1963). Various constituents of Staphylococcus aureus have been separated on Sephadex, namely, teichoic acid, D-alanine, N-acetylglucos-amine, and N-acetylglucosaminylribitol (Sanderson et al., 1962). 

The terminal N-acetylneuraminic acid was cleaved off with neuraminidase to yield neutral carbohydrate compounds. The structures shown above only differ in the labeled and jff-1,4-linkage between galactose and N-acetylglucos-amine in the lactosamine residue of this tri-anteimary ohgosaccharide [216]. Neither isomers can be separated with conventional RPLC techniques. 

The structure of several other K-antigens have been reported by Jann and co-workers. Of these K5 deserves mention as a further example of a non-immunogenic K-antigen. The K5 polysaccharide composed of repeating disaccharide units of al—4-linked glucuronyl pi—4 N-acetylglucos-amine closely resembles desulpho-heparin, a precursor of the natural blood anticoagulant heparin. 

Hayes, B.K. Freeze, H.H. Varki, A. Biosynthesis of oligosaccharides in intact Golgi preparations from rat liver. Analysis of N-linked glycans labeled by UDP-[6- H]N-acetylglucos-amine./. Biol Chem. 1993, 268, 16139-16154. 

Guillen E, Abeijon C, Hirschberg CB. Mammalian Golgi apparatus UDP-N-acetylglucos-amine transporter molecular cloning by phenotypic correction of a yeast mutant. Proc. Natl Acad. Sci. U.S.A. 1998 95 7888-7892. 

Recall that chitin is a poly-P-l,4-2-deoxy-2-N-acetylglucos-amine and has a structure similar to that of cellulose more or less deacetylated forms also occur. Naturally occurring chitins are almost always copolymers of theoretical chitin and of the deacetylated forms the most completely deacetylated polymer is chitosan. This latter is not natural it was obtained in 1859 when treating chitin with boiling potash solution. An 80% deacetylated chitin produces a chitosan with a molecular weight of about... 

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