Glucosyl 2-acetamido-2-deoxy

The amino sugar counterparts of D-glucuronic acid and nonsulfated L-iduronic acid in heparin are either N-acetylated, or nonsulfated at C-6, or both. 2-Acetamido-2-deoxy-D-glucosyl residues account for only a minor proportion of the total hexosamine in heparin, and are especially low in beef-lung preparations (see Table II).8,138,147 -149 In contrast, they... 

Whereas a major proportion of the 2-acetamido-2-deoxy-D-glucosyl residues is probably nonsulfated at C-6 (C-sulfation is expected to require prior N-sulfation),23 various degrees of C-sulfation have been reported for N-acetylated regions of heparan sulfates,148,149 and a 6-C-sul-fated, N-acetylated disaccharide was isolated from heparanase digests of heparan sulfates.114,115... 

The scope of the deamination reaction was extended to the characterization of heparin segments containing 2-acetamido-2-deoxy-D-glucosyl residues by removing (by hydrazinolysis) the N-acetyl groups and cleaving with nitrous acid (at pH 4) the otherwise resistant segments.113,232... 

Structure 34 was proposed for a trisaccharide composed of d-glucose, D-galactose, and 2-acetamido-2-deoxy-D-galactose residues. The D-glucosyl group and the D-galactosyl residues are the same as in disaccharide 32. That the 2-acetamido-2-deoxy-D-galactose residue is linked to 0-3 was indicated by color reactions and the fact that this... 

Keratan sulfate consists of a (l—>3)-0-/3-D-galactopyranosyl-(l— 4)-0-2-acetamido-2-deoxy-/3-D-glucopyranosy 1 repeating-unit containing 40% of galactosyl residues and >70% of 2-acetamido-2-deoxy-D-glucosyl residues esterified at C-6 by sulfate. 

Formation of the 2-Acetamido-2-deoxy-/ -D-glucosyl - L-Asparagine Linkage... 

A half-chair conformation of a crystalline monosaccharide has not been observed. A half-chair conformation for the fourth 2-acetamido-2-deoxy-/3-D-glucopyranosyl residue (residue D) in the lysozyme substrate has not been detected, although, on the basis of model fitting, its presence has been suggested (see p. 96). 2-Acetamido-2-deoxy-/3-D-glucosyl groups were added to a molecular model constructed by use of data obtained from the nature of the enzyme-trisaccharide complex it was implicit that the lifetime of the half-chair conformation would be quite short. 

In the first Section, the dolichol pathway of protein glycosylation is introduced, and the reader is made familiar with the various reactions in the formation of the lipid and carbohydrate moieties of lipid-linked saccharides. Three different classes of compound are known so far (a) isoprenoid alcohol esters of monosaccharide monophosphates, such as D-mannosyl and D-glucosyl (dolichol phosphate), (b) such isoprenoid alcohol esters of saccharide diphosphates as dolichol diphosphate linked to 2-acetamido-2-deoxy-D-glucose and to oligosaccharides, and (c) retinol (D-mannosyl phosphate). The dolichol-linked sugars occur in all eukaryotes. 

The dolichol-linked D-mannosyl, D-glucosyl, and 2-acetamido-2-deoxy-D-glucosyl residues are used in the glycosylation of proteins and in the biosynthesis of D-m an nan.2,35 GlcNAc-PP-Dol may also play a role in the synthesis of glycosaminoglycans. Reaction 4 is the first step in the formation of lipid-linked precursors for cellulose.46... 

The 2-amino-2-deoxy-D-glucosyl phosphate linkage is very labile to acid consequently, the teichoic acid is hydrolyzed under mild conditions to a fragment which is apparently44 (43) or (44). Study of this compound should establish which hydroxyl group of the 2-acetamido-2- deoxy-D-glucose residue bears the phosphodiester group. The alanine ester residues (84a) Unpublished work of the authors with Mr. D. Button. 

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