NeuSAc N-acetylneuraminic acid

Scheme L Synthesis of a2,64inked sialyl-N-acetyllactosamine using a one-pot multi-enzyme system with in situ regeneration of CMP-Neu5Ac. Abbreviations for enzymes CSS, CMP-sialic acid synthetase NMK, nucleoside monophosphate kinase PK, pyruvate kinase PPase, pyrophosphatase. Abbreviations for compounds PEP, phosphoenolpyruvate ADP, adenosine 5 -diphosphate ATP, adenosine 5 -triphosphate CMP, cytidine 5-monophosphate CDP, cytidine 5 -diphosphate CTP, cytidine 5-triphosphate LacNAc, N-acetyllactosamine NeuSAc, N-acetylneuraminic acid PPi, inorganic pyrophosphate.

Sialic acids are a family of 3-deoxy-2-ulosonic acids found most frequently as a-glycosidically linked terminal residues of glycoproteins and glycolipids. The most abundant sialic acid is N-acetylneuraminic acid (5-acetamido-3,5-di-deoxy-D-glycero-D-galacto-nonu osonic acid, NeuSAc, 1), which was first isolated in the 1930s. To date, 36 sialic acids have been isolated, many of which are 0-acetylated derivatives of N-acylated neuraminic acid [1]. 

Sialic acid is the general name of a mily of nine-carbon sugars, which are N- and 0-acyl derivatives of neuraminic add, 5-amino-3,5-dideoxy-D-gi ero-D-ga/ac/o-2-nonulopyranosic add such as 5-N-acetylneuraminic acid (NeuSAc, 1) which is the most natural occurring sialic add [1]. 

Scheme 11 N-Acetylneuraminic acid (NeuSAc) and 3-deoxy-D-ma o-oct-2-ulosonic acid (Kdo).

C,H,7N0 Mr 267.25. An amino sugar acid isolated from gangliostdes and named by Klenk. N. is unstable and cyclizes spontaneously to furnish a pyrroline derivative. However, it is widely distributed in N- and O-acylated forms. N-Acetylneuraminic acid (NeuSAc, Neu/VAc, NANA) C,H NO Mr 309.27, mp. 185-187°C, [a]o -33 (HjO). 

Higher organisms and some bacteria utilize PEP-dependent N-acetylneuraminic acid synthase (NeuS EC 2.5.1.56) for the generation of sialic acids and related compounds (Scheme 17.3) [17, 21]. In mammaHan cells, NeuSAc is synthesized from the phosphorylated ManNAc-6-phosphate precursor by the PEP-dependent N-acetylneuraminic acid 9-phosphate synthase (Neu9PS EC 2.5.1.57). By simultaneous release of inorganic phosphate from the enol ester upon C-C bond formation, the additions are essentially irreversible. 

A key intermediate in the biosynthesis of glycoconjugates is the sugar nucleotide cytidine-5 -monophospho-N-acetylneuraminic acid (CMP-NeuSAc). To check its... 

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