Glucosamine, amides

Amino sugars, such as o-glucosamine, have an OH group leplaced by an -NH2. The N-acetyl amide derived from o-glucosamine is the monosaccharide unit from which chitm, the hard crust that protects insects and shellfish, is made. Still otheramino sugars are found in antibiotics such as streptomycin and gentamicin. 

A bacterial phosphatidylinositol specific phospholipase C (PI-PLC) had been available for many years before it was demonstrated to strip a number of membrane-bound proteins from eukaryotic cell surfaces [1], Such proteins are anchored by a PI moiety in which the 6 position of inositol is glycosidically linked to glucosamine, which in turn is bonded to a polymannan backbone (Fig. 3-10). The polysaccharide chain is joined to the carboxyl terminal of the anchored protein via amide linkage to ethanolamine phosphate. The presence of a free NH2 group in the glucosamine residue makes the structure labile to nitrous acid. Bacterial PI-PLC hydrolyzes the bond between DAG and phosphati-dylinositols, releasing the water-soluble protein polysac charide-inositol phosphate moiety. These proteins are tethered by glycosylphosphatidylinositol (GPI) anchors. 

Tungsten aryloxo complexes have been shown to catalyze the intramolecular metathesis reactions of di- and tri-substituted co-unsaturated glucose and glucosamine derivatives to yield bicyclic carbohydrate-based compounds containing 12- and 14-membered rings [108,214,215]. An example is shown in Eq. 37. The tolerance for amides and esters is noteworthy, as are the yields and the size of the rings that are formed. 

Glutamine is one of the principal combined forms of ammonia that is transported throughout the body (Chapter 24). Glucosamine 6-phosphate synthase, which catalyzes the reaction of Eq. 20-5, is an amido-transferase of the N-terminal nucleophile hydrolase superfamily (Chapter 12).31 It hydrolyzes the amide... 

From the conclusion that 12 0 and 16 0 are quantitatively bound to hydroxyl groups of amide-linked 3-OH-14 0, it follows that, of the fatty acids present in Salmonella lipid A, only (R)-3-hydroxytetradecanoyl residues (4 mol/2 moles glucosamine) are... 

O-Acetyl- -dimethylamid-ethylester XII/2, 567 O-Acetyl- -dimethylester E2, 488 O-Acetyl- -D-galactosyl-(6)-ester XII/2, 557 N-Acetyl-glucosamin-6- XII/2, 210 O-Acetyl- -a-D-glucosyl-(l)-ester XII/2, 557 -(2-acetyl-hydrazid)-diethylester E2, 621 -[acetyl-(2-hydroxy-ethy )-amid]-diisopropylester XII/2, 482... 

Figure 18.17 Conversion of fructose-6-phosphate to N-acetylglucosamine. Note that the amino group of glucosamine comes from the amide residue of glutamine.

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