NeuAc N-acetylneuraminic acid

Table 4.3.3 Normal reference values of free and bound N-acetylneuraminic acid (NeuAc) in human urine (adapted from Waters [23])...

The enzymatic preparation of the activated sugar nucleotide may also involve a cofactor regeneration system. An example of this is an economic one-pot procedure, in which N-acetylneuraminic acid (NeuAc) is generated in situ from IV-acetylmannosamine (ManNac) and pyruvate with sialic acid aldolase and then converted irreversibly to CMP-NeuAc ([14], see also Sec. III). 

Anion of N-Acetylneuraminic acid (NeuAc), one of the Sialic acids (Sia), nine carbon sugars found in many glycoproteins. 

NeuAc, N-acetylneuraminic acid Cer, ceramide Gic, giucose Gai, gaiactose. -p, site of deficient enzyme reaction. 

Fig. 1.4.7. Early steps in combinatorial ganglioside biosynthesis [9]. The sites of (indirect) inhibition by 11 and 12 are indicated. Abbreviations Cer, ceramide, N-acylsphingosine Clc, glucose Gal, galactose GalNAc, N-acetylgalactosamine NeuAc, N-acetylneuraminic acid SAT, sialyltransferase GalNAcT, N-acetylgalactosaminyltransferase ...

N-Acetylneuraminic acid aldolase (NeuAc aldolase) is commercially available and has been the subject of much attention [49]. NeuAc aldolase catalyzes the aldol reaction between pyruvate and mannose or mannose derivatives. The enzyme activates the donor as its enamine, similar to the Type I aldolase described above (Scheme 5.21). The enzyme has been used for the synthesis of aza sugars and var-... 

CMP-N-acetylneuraminic acid (CMP-NeuAc). CMP-N-acetylneuraminic acid has been prepared enzymatically on small scales (> 0.5 mmol) from CTP and NeuAc, under catalysis by CMP-NeuAc synthetase (EC 2.7.7.43) [131l An improvement in this procedure, involving in situ production of CTP from CMP under adenylate kinase and pyruvate kinase catalysis, is suitable for multigram-scale synthesis11321. Adenylate kinase catalyzes the equilibration of CTP and CMP to CDP, which is subsequently phosphorylated by pyruvate kinase to provide CTP. A one-pot synthesis of CMP-NeuAc based on this procedure involves the in situ synthesis of NeuAc from N-acetylmannosamine and pyruvate, catalyzed by sialic acid aldolase (Fig. 11.3-12)[10S1. Chemical syntheses of CMP-NeuAc have also been reported11421. 

N-Acetylneuraminic acid aldolase catalyzes the reversible aldol condensation of pyruvate (23) and N-acetylmannosamine (22 ManNAc) to form N-acetylneuraminic acid (24 NeuAc N-acetyl-5-amino-3,5-dideoxy-D-glycerogalacto-2-nonulopyronic acid Scheme 6).80-83 In vivo the enzyme has a catabolic function and the equilibrium for this reaction is near unity the presence of excess pyruvate can shift this equilibrium. NeuAc and other derivatives of neuraminic acid are termed sialic acids. These compounds are found at the termini of mammalian glycoconjugates and play an important role in cellular recognition.84-89 The production of analogs of NeuAc is a point of great interest to synthetic and medicinal chemists. The enzymatic approach has not been fully explored but it may be a practical alternative to the chemical synthesis of certain sialic acids.89... 

V-Acetylneuraminic acid (NeuAc) aldolase (E.C. 4.1.3.3) catalyzes the formation of NeuAc from yV-acetylmannosamine and pyruvate (Scheme 11). The sialic acids are key cell-surface determinants of mammalian glycoconjugates. We and others have prepared V-acetylneuraminic acid (32) via a NeuAc aldolase-catalyzed condensation between N-acetylmannosamine and pyruvate. A number of derivatives of sialic acid have been prepared using derivatives of mannose (33-35). 

We found that the enzyme preparation converted N -acetylneuraminic acid almost completely to CMP-NeuAc (90% yield, FPLC) at pH 9 and with the starting concentrations of 10 mM of NeuAc and 15 mM of CTP. Moreover, the enzyme preparation showed only a slight decrease of activity after three separate uses for a total reaction time of 90 h at 30 C (49). 

Fuc = fucose, GIcNAc = N-acetylglucosamine, GalNAc = N-acetylgalactosamine, NeuAc = N-acetylneuraminic acid. Together with sialyl-a-(2->-3)-lactose. ... 

N acetylglucosamine (GlcNac) F, fucose M, mannose Gal, galactose NeuAc, N-acetylneuraminic acid (sialic acid). Table 2. Examples of monosaccharide inhibitors of lectins. ... 

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