N-acetylneuraminate

N-Acetylneuraminic acid aldolase (or sialic acid aldolase, NeuA EC 4.1.3.3) catalyzes the reversible addition of pyruvate (2) to N-acetyl-D-mannosamine (ManNAc (1)) in the degradation of the parent sialic acid (3) (Figure 10.4). The NeuA lyases found in both bacteria and animals are type I enzymes that form a Schiff base/enamine intermediate with pyruvate and promote a si-face attack to the aldehyde carbonyl group with formation of a (4S) configured stereocenter. The enzyme is commercially available and it has a broad pH optimum around 7.5 and useful stability in solution at ambient temperature [36]. 

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

The c.d. spectra of a number of other derivatives have been measured as models for the linkages found in oligomers. Spectra of the methyl a-and )8-D-ketopyranosides of N-acetylneuraminic acid are given in Fig. 29. They do not differ substantially from the c.d. spectra for the fundamental sugars, except that the a-ketopyranoside has a positive c.d. band of low intensity at 250 nm. These types of bands occur from time to time for still obscure reasons, as discussed for carboxyl derivatives. 

The c.d. spectra are also available for a few oligosaccharides that contain N-acetylneuraminic acid. " These spectra depend on the intersaccharide linkages and the state of ionization of the carboxyl group, but no systematic scheme has yet been set up to derive configurational information from the c.d. spectra. Of particular interest is the c.d. spectrum of beef ganglioside, which fully differentiates the amide mr, amide tttt, and carboxylate nir c.d. bands. 

IonPac KC-811 column separated the labile compounds N-acetylneuraminic acid and N-glycolylneuraminic acid released by mild acid hydrolysis of bovine vitronectin.245 Sialic acid is extremely labile to conditions of handling and must be released by mild acid hydrolysis.246 Derivatization with phe-nylisothiocyanate and separation by reversed phase chromatography was found useful in analysis of hexosamines from gastric mucosa.247 A review on separation of sugars and other carbohydrates which covers many important aspects is available.248... 

Ogawa, H. K., Takeuchi, Y., Uchibori, H., Matsumoto, I., and Seno, N., Determination of N-acetylneuraminic acid and N-glycolylneuraminic acid in glycoproteins by high-performance liquid chromatography without derivatization, /. Chromatogr., 612, 145, 1993. 

Thus, an alkene can be considered as a masked ketone that can be unmasked by ozonolysis. This is illustrated by the synthesis of N-acetylneuraminic acid via the ozonolysis of the precursor acrylic acid in THF/aqueous media (Eq. 3.22). The use of aqueous media facilitated the solubility of the polyhydroxyacids.92... 

Phosphonic acid analogues 8.2 and 8.3 of both KDN and N-acetylneuraminic acid have been synthesized using the indium-mediated coupling of the lower carbohydrates with dimethyl 3-bromopropenyl-2-phosphonate (8.4) in water (Scheme 8.9).124... 

C H19N09-2H20 5-Acetamido-3,5-dideoxy-D-gh/eero-/ -D-galacto-nonulopyran-osonic acid, dihydrate (N-acetylneuraminic acid, dihydrate) (sialic acid, dihydrate) SIALAC 31 350... 

Mahmoudian, M., Noble, D., Drake, C.S. etal. (1997) An efficient process for production of N-acetylneuraminic acid using V-acetyl neuraminic acid aldolase. Enzyme and Microbial Technology, 20 (5), 393—400. 

Naphthalene-2,3-dicarboxaldehyde Nicotinamide adenine dinucleotide N-Acetylneuraminic acid 4-Fluoro-7-nitrobenzoxadiazole Naphthalene-2,3-dicarboxaldehyde Nondestructive readout Near infrared Near infrared fluorescence Nuclear magnetic resonance 2-Nitrophenyl oxalate 1,1 -Oxalyldiimidazole Polycyclic aromatic hydrocarbon Principal component analysis Photosensitized chemiluminescence Pentachlorophenyl oxalate Polymerase chain reaction... 

Takahashi and coworkers described an effective sialylation method utilizing the N-Fmoc, N-Troc and N-trichloroacetyl-P-thiophenyl sialosides (Scheme 4.6d) [167]. It was found that the N-Troc derivative of N-acetylneuraminic acid performed better than the corresponding N-Fmoc derivative. An N-Troc P-thiosialoside was applied for the synthesis of glycosyl amino acids by one-pot glycosylation [167]. Importantly, it was found that the N-Troc protecting group could be converted into an acetamido moiety without causing racemization of the peptide. 

It has been observed that the neuraminic acid linkages can also be conveniently analyzed by the methylation technique.33,34 Some important fragments, the origins of which were confirmed by deuteriumlabelling experiments,33 are shown for two common, N-acetylneura-minic acid derivatives, namely, the terminal sugar derivative 10 and the 8-O-substituted N-acetylneuraminic acid (11). 

Fig. 3.—Mass Fragmentography of Methylated Neuraminic Acids. [Detection at m/e 274 A, disialosyl-lactosylceramide B, the disialosyl ganglioside isolated C, B after treatment with neuraminidase D, the fraction containing the trisialosyl ganglioside. Detection at m/e 330 E, the disialosyl ganglioside F, the trisialosyl fraction. The peaks identified are (1) the permethylated (terminal) N-acetylneuraminic acid, and (2) the 8-O-acetyl (8-O-substituted) derivative of the methylated N-acetylneuraminic acid. Conditions 1% of SE-30, at 240°. Reproduced, by permission, from Ref. 80.]...

Gangliosides branched oligosaccharide chains terminating in the 9-carbon sugar, sialic acid (N-acetylneuraminic acid, NANA)... 

The neuraminic acids (also called sialic acids), which occur in the terminal positions of carbohydrate moieties of many glycoproteins and ganglio-sides, must be hydrolyzed under very mild conditions. For example, hydrolysis with 0.01 M hydrochloric acid for 30 min at 100° causes 20% decomposition of N-acetylneuraminic acid. Sialic acids are more tolerant to methanolysis they may also be removed enzymically. 

N-acetylneuraminic acid (sialic acid, 5), is a characteristic component of glycoproteins. Other acidic monosaccharides such as D-glu-curonic add, D-galacturonic add, and liduronic add, are typical constituents of the glycosa-minoglycans found in connective tissue. 

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