Neuraminic acid 9-phosphate

A -acetyl-D-neuraminic acid is biosynthesized from A -acetyl-D-mannosamine and phosphoenol pyruvate, catalyzed by N-acetyl-D-neuraminic acid synthase. The first step involves the addition of an electron pair from the double bond of the phosphoenol pyruvate to the aldehyde group to give an aldol-type condensation (see Fig. 10.8A). The product is the nine-carbon sugar acid, A -acetyl-D-neuraminic acid [23]. In some instances the enzyme requires A-acetyl-D-mannosamine-6-phosphate as the substrate and forms A-acetyl-D-neuraminic acid-9-phosphate. Various hydroxyl groups on C-4, -7, -8, and -9 can be acetylated by specific acetyl transferases using acetyl CoAas the donor. KDO (2-keto-3-deoxy-D-mannooctulosonic acid) is biosynthesized by a very similar condensation between D-arabinose-5-phosphate and pyruvic acid, catalyzed by KDO synthase (see Fig. 10.8B) [24]. 

Warren, L., and Felsenfeld, H., 1961, N-Acetylmannosamine-6-phosphate and A-acetyl-neuraminic acid -9-phosphate as intermediates in sialic acid biosynthesis, Biochem. Biophys. Res. Comm. 5 185. 

Fraction Galactose N-acetyl- galactosamine. V-acetyl- neuraminic acid Phosphate... 

The biosynthesis of Kdo and neuraminic acid is known to involve enol-pyruvate phosphate and D-arabinose or 2-acetamido-2-deoxy-D-mannose, respectively. Nothing is known about the biosynthesis of all the other glycu-losonic acids. One interesting problem is, for example, whether the two 5,7-diamino-3,5,7,9-tetradeoxynonulosonic acids are synthesized analogously to neuraminic acid, from a three- and a six-carbon fragment, by modification of neuraminic acid on the sugar nucleotide level, or by a third, less obvious route. 

C-6,209,214 anhydro sugars,branched monosaccharides, fluori-nated amino sugars,difluorinated monosaccharides, and fluorinated monosaccharide phosphates,and phosphonates have been described. Further progress has been achieved in the synthesis and n.m.r.-spectral analysis of fluorinated avermectin Bu, tylono-lide, and neuraminic acid derivatives. " ... 

Figure 2.19 Sialylation ofN-acetyl lactose by cytidyl monophosphate-N-acetylneuraminic acid using Of 2,3-neuraminic acid transferase as catalyst (upper box). Regeneration of the sugar nucleotide is shown in the lower box. CMP is converted into CTP in two steps using two different kinases. In the final step CMP-A -acetylneuraminic acid is synthesised from CTP and A -acetylneuraminic acid (sialic acid) using the appropriate synthetase. The formed pyrophosphate is converted into inorganic phosphate. Altogether five different enzymes are involved in the process.

A-Acetyl neuraminic acid aldolase [from Clostridium perfringens, A-acetylneuraminic acid pyruvate lyase] [9027-60-5] [EC 4.1.3.3]. Purified by extraction with H20, protamine pptn, (NH4)2S04 pptn, Me2CO pptn, acid treatment at pH 5.7 and pptn at pH 4.5. The equilibrium constant for pyruvate + n-acetyl-D-mannosamine ++ /V-acetylneuraminidate at 37° is 0.64. The Km for A-acetylneuraminic acid is 3.9mM in phosphate at pH 7.2 and 37°. [Comb and Roseman Methods in Enzymology 5 391 1962). The enzyme from Hogg kidney (cortex) has been purified 1700 fold by extraction with H20, protamine sulphate pptn, (NH4)2S04 pptn, heat treatment between 60-80°, a second (NH4)2S04 pptn and starch gel electrophoresis. The Km for A-acetylneuraminic acid is 1.5mM. [Brunetti et al. JBC 237 2447 1962). 

T. J. Martin and R. R. Schmidt, Efficient sialylation with phosphites as leaving group, Tetrahedron Lett. 33 6123 (1992) T. J. Martin, R. Brescello, A. Toepfer, andR. R. Schmidt, Synthesis of phosphites and phosphates of neuraminic acid and their glycosyl donor properties— convenient synthesis of GM3, Glycoconjugate J. 70 16 (1993), and references therein. 

When CMP-iV-acetyl neuraminic acid synthetase (EC 2.7.7.43) of Haemophilus influenzae, polyphosphate kinase and CMP kinase were added to the reaction mixture containing equimolar concentrations (15 mM) of CMP and V-acetyl neuraminic acid, and PolyP (150 mM in terms of phosphate), CMP-iY-acetyl neuraminic acid was synthesized up to 67 % yield (Ishige et al, 2001). 

A number of functional sialyl Lewis mimetics have been synthesized. Their activities in vitro are equal or even better than those of the tetrasac-charide itself. To overcome synthetic problems, efficient stereoselective glycosylations as well as new chemoenzymatic methods for C-C bond formations had to be developed. The substitution of neuraminic acid by (5)-phenyl- and (5)-cyclohexyl lactic acid, as less flexible glycol acid residues, turned out to be very successful [10]. Also, a phosphate and a sulfate group, respectively, mimic neuraminic acid without loss of activity [11]. (5)-Cyclohexyl lactic acid-mimetic 2 shows a more than ten-fold efficacy compared with sialyl Lewis, whereas the corresponding (/ )-isomer 3 is almost inactive [10]. The deviating orientation of the carboxylic acid functionality compared to the bioactive sialyl Lewis conformation leads to the examined loss of activity. It was shown by transfer-NOE measurements of the corresponding E-selectin complexes that the coordinates of the bioactive conformation of sialyl Lewis and of compound 2 are similar. Con.se-quently structure 2 should bind to E-selectin in the same manner as that of sialyl Lewis [ 10a, b]. 

On the other hand, the sugar moiety of the glycosphingolipids represents the hydrophilic part of the molecule. The solubility in water is also dependent on the number of monosaccharide residues bound in the molecule. Furthermore, such strongly anionic components as neuraminic acids, and sulfate or phosphate groups, influence the ratio of the solubility in water and fat. These two kinds of solubility characteristics are probably essential in the biological roles of the glycosphingolipids when they function as biomembrane components. 

Szabo and his colleagues have prepared 3-deoxy-D-crj f/iro- and U-threo-hcx-2-ulosonic acid 5-phosphate in the ratio 2 1 as illustrated in Scheme 1. The products were isolated in 37 and 23% yield, respectively, as their magnesium salts.In parallel fashion, Russian workers have developed a synthesis of 3-deoxyaldulosonic acids as depicted in Scheme Studies by n.m.r. spectroscopy of ot- and /3-A-acetylneuraminic acid derivatives and determination of /c-i-H-3 e values allowed the conclusion that, in cytidine 5-phospho-iV-acetyl-neuraminic acid, a key intermediate in the biosynthesis of glyconoconjugates, the neuraminic acid moiety has the 3-configuration. ... 

The extraparotid saliva of Macaque monkeys contains a glycoprotein (mol. wt. 9.6 X 10 ) capable of inhibition of the precipitation of calcium phosphate. The major glycoproteins obtained from Bonnet monkey cervical mucous of the peri-ovulatory and of the pre-menstrual phases differ mainly in the point of linkage of the terminal neuraminic acid residues and of the substitution of the... 

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