UDP-A-acetylglucosamine

Figure 17-5. Synthesis of the mannose 6-phosphate recognition marker. R represents the high-mannose oligosaccharide of newly synthesized lysosomal enzymes. Reaction 1 is catalyzed by UDP-A,-acetylglucosamine lysosomal enzyme Ar-acetylglucosaminyl-1 -phosphotransferase. Reaction 2 is catalyzed by iV-acetylglucosamine-l-phosphodiester-iV-ace tylgluco saminidase.

Bao M, Elmendorf BJ, Booth JL, Drake RR, Canfield WM. Bovine UDP-A-acetylglucosamine lysosomal-enzyme A-acetyl-glucosamine-1-phosphotransferase. 11. Enzymatic characteriza-hon and identification of the catalytic subunit. J. Biol. Chem. 1996 271(49) 31446-31451. 

An enzyme instrumental in bacterial cell wall biosynthesis is UDP-A -acetylenolpyruvylglucosamine reductase (MurB). MurB catalyzes the NADPH-dependent reduction of enolpyruvyl-UDP-A -acetylglucosamine (enolpyruvyl-UDP-GlcA Ac) to the corresponding D-lactyl compound UDP-ALacetylmuramic acid (UDP-Murmc) (Equation (12)). 

Single-stranded left-handed / helix Trimeric LpxA-like enzymes UDP A -acetylglucosamine acyltransferase UDP A -acetylglucosamine acyltransferase... 

Fig. 7. Biosynthesis of endotoxin in E. coli. The first step (1) in the pathway is catalyzed by UDP-A -acetylglucosamine (UDP-GlcNAc) acyltransferase (LpxA). (2) The committed step is catalyzed by the LpxC deacetylase, followed by (3) a second acyltransferase (LpxD). (4) Lipid X is generated by the removal of UMP from UDP-2,3-diacyl-GlcN by an unknown enzyme. (5) Lipid X and UDP-2,3-diacyl-GlcN are then condensed together by LpxD to form Lipid IV. (6) A 4 -kinase phos-phorylates the disaccharide to produce lipid IV. (7) Two consecutive additions of KDO by KdtA, and two 0-acylations by (8) HtrB and (9) MsbB yield KDOj-lipid A. Subsequent addition of core sugars and 0-antigen chains (not shown) yield the mature LPS.

The mechanism of UDP-A -acetylglucosamine 2-epimerase, an important enzyme used by bacteria for preparing activated UDP-JV-acetylmannosamine residues for use in cell wall formation, has been investigated using an 0-labelled UDP-GlcNAc derivative and shown to involve the intermediacy of 2-acetamido-2-deoxy-D-glucal. ... 

Epimerisations of this type are uncommon in sugar nucleotide systems, and because of the hindered nature of C-2 they necessarily proceed by a mechanism somewhat different from the reactions described above. The most important example is the formation of N-acetylmannosamine from UDP-A/-acetylglucosamine, as a step in the synthesis of the sialic acids in bacteria and animals. 

Figure 1.9 Structure of UDP-AAacetylmuramic Acid and its Synthesis from UDP-A/-acetylglucosamine and Phosphoenolpyruvate...

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