A-Acetyl-n-glucosamine

Biosynthetic investigations show that the hyaluronate chain is assembled by the alternate incorporation of preformed A -acetyl-n-glucosamine and D-glucuronate units. In descriptive scientific nomenclature, the units are 2-acetamido-2-deoxy-/3-D-glucopyranosyl and /3-D-glucopyranosyluro-nate, respectively. 

Complete hydrolysis of hyaluronate by a crude testicular extract produces A -acetyl-n-glucosamine and n-glucuronic acid. For partial hydrolysis of the polysaccharide, pneumococcal and testicular hyaluronidases are useful. 

It is not definitely known whether the a or the /3 anomer of AT-acetyl-n-glucosamine 1-phosphate is involved in this isomerization of A -acetyl-D-glucosamine 1-phosphate. However, an extremely acid-labile A -acetyl-n-glucosamine phosphate did contaminate some of the A -acetyl-... 

Uridine diphosphate A -acetyl-n-glucosamine has been isolated and structurally characterized. The compound can be obtained from a nucleotide fraction of yeast by elution from a Dowex-1 anion-exchange column, and from guineapig livers by precipitation as the barium salt. ... 

A uridine pyrophosphate derivative of Ai -acetyl-n-glucosamine which contains an extra phosphate group has been isolated from a hot-water extract of hen oviducts. Uridine 5-phosphate and uridine 5-pyrophosphate have been recovered from acid hydrolyzates of this compound. A diphosphate ester of A-acetyl-n-glucosamine can also be obtained from acid hydrolyzates of this uridine compound. Because of the catalytic activity of phospho-A -acetyl-n-glucosamine mutase toward it, it is probably AT-ace-tyl-D-glucosamine 1,6-diphosphate. 

Uridine diphosphate A -acetyl-n-glucosamine can undergo enzymic pyrophosphorolysis in the presence of pyrophosphate, to form uridine-5-... 

D-Fructose 6-phosphate and ammonia interact to produce hexosamine when they are added to a fraction of pig-kidney protein together with catalytic amounts of A -acetyl-n-glucosamine 6-phosphate. Neither L-glutamine nor L-asparagine can replace ammonium sulfate as a nitrogen source in this system, and D-fructose 6-phosphate cannot be replaced by D-fructose, n-xylose, n-glucose, or D-ribose. The presence of N-acetyl-D-glucosamine is also essential for this reaction. 

Thus, the nonulosaminic acids were formulated as aldol condensation products of a hexosamine with pyruvic acid. This speculative concept received its first support with the isolation of A -acetyl-n-glucosamine as a degradation product of A -acetylneuraminic acid. These degradations employed nickel acetate plus pyridine or mild alkah for ten minutes. Besides A -acetyl-n-glucosamine and a number of unidentified degradation products, pyruvic acid was produced and was isolated as its (2,4-di-nitrophenyl) hydrazone. 

D-Glucosamine is an example of an amino sugar. In many instances the amino group is acetylated as in A-acetyl-n-glucosamine. A-Acetylmuramic acid is an important component of bacterial cell walls (Section 24.10). 

Die Lado-N-biose I (146) kristallisiert als Dihydrat der a-Form in feinen Nadeln vom Schmelzpunkt 166 bis 167° und der spezifischen Drehung [a] 0 — + -f- 14°. Sie besteht aus A -Acetyl-u-glucosamin... 

We propose that the first step in NDP-kasugamine biosynthesis is 2-epimeriza-tion of the postulated UDP-A -acetyl-D-glucosamine precursor, which is suggested by the similarity of the KasQ protein with known UDP-(Af-acetyl-)D-glucosamine 2-epimerases and catalyzes the conversion to UDP-N-acetyl-D-mannosamine. To... 

This enzyme [EC 2.4.1.16], also known as chitin-UDP N-acetylglucosaminyltransferase, catalyzes the reaction of UDP-A-acetyl-D-glucosamine with [(1,4)-(A-ace tyl-jS-D-glucosaminyl)] to produce UDP and [(l,4)-(A-acetyl-j8-D-glucosaminyl)]( +i). The enzyme ultimately converts UDP-A-acetyl-D-glucosamine into chitin and UDP. 

Vasella has applied the concept of anomeric anion stabilization by a nitro group to the /3-D-JV-acetyl-D-glucosamine derivative 177, available in four steps from N-acetyl-n-glucosamine [52] (Scheme 39). Reaction of the tetraethylammonium nitronate derived from 177 with aldehyde 178 provides anti-179 which then undergoes stereoselectively reduction (see Sect. 2.2.1) to provide -C-glycoside 180, intermediate in a synthesis of N-acetyl-neuraminic acid. 

Hydrolyzes chitobiose and higher analogs and protein derivatives by removing Af-acetyl-n-glucosamine from the non reducing end A /S-D-glucuronide + HzO — alcohol + D-glucuronic acid... 

---