N-Acetylneuraminic acid 9-phosphate

A synthetase purified from liver and submaxillary gland produces N-acetylneuraminic add 9-phosphate and Pj by condensing acetylmannosamine-6-phos-phate and phosphoenolpyruvic acid. Sialic acid is formed by the action of phosphatase on N-acetylneuraminic acid-9-phosphate. The biosynthetic pathway of sialic acid is summarized in Fig. 3-32. 

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. 

N-acetylneuraminic acid 9-phosphate - - Pi N-Acetylneuraminic acid 9-phosphate - N-acetylneuraminic acid -1- Pi... 

Warren, L., and H. Felsenfeld N-acetylmannosamine-6-phosphate on N-acetylneuraminic acid-9-phosphate as intermediates in sialic acid biosynthesis. Biochem. biophys. Res. Commun. 6, 185 (1961). 

CMP-KDO synthetase (cytidine-5 -triphosphate cytidine-5 -mon-ophosphate-3-deoxy-D-manno-octulosonate cytidylyltransferase), the next enzyme in the pathway, catalyzes the formation of the nucleotide sugar, CMP-KDO from CTP and KDO. This enzyme was first studied by Ghalambor and Heath (IT). We have purified this enzyme to homogeneity (27). T i apparent K values for CTP nd KDO in the presence of 10 mM Mg were determined to be 2 x 10 M and 2.9 x 10 M, respectively. The enzy tic reaction was dependent upon the addition of CTP, KDO and Mg but did not require a reducing agent. The formation of CMP-KDO was not inhibited by the addition of CDP, CMP, KDO-8-phosphate or N-acetylneuraminic acid to the complete reaction mixture. In agreement with Ghalambor and Health (17), neither KDO-8-phosphate nor N-acetylneuraminic acid could substitute for KDO in the reaction mixture. Pyrophosphate, one of the end products, is a weak inhibitor of the reaction with an apparent Ijq value of 5.0 mM. The addition of CMP,CD or any of the other mono- or di-nucleotides did not inhibit the reaction. 

The synthesis of the methyl ester of 9-0-glycyl-N-acetylneuraminic acid has been reported by Derevitskaya et al. (1965 b). The methyl ester of N-acetylneuraminic acid was coupled with N-benzyloxycarbonylglycine in the presence of dicyclohexylcarbodiimide subsequently the benzyloxycarbonyl group was removed by hydrogenolysis. The 9-phosphate esters of N-acetylneuraminic acid and N-glycolylneuraminic acid were prepared enzymatically (Roseman et al. 1961, Warren and Felsenfeld 1961, Watson et al. 1966a,b). Also a chemical... 

The a- and P-glycopyranosyl phosphates of 3-deoxy-D-ma no-2-octulosonic acid have been prepared from Kdo as inhibitors of 3-deoxy-D-/nowio-2-octuloso-nate-8-phosphate synthase, which occurs in Gram-negative bacteria. iV-Acetyl-neuraminic add has been 0-alkylated at C-4 by selective alkylation of an 8,9-0-isopropylidene derivative, and treatment of the a-benzyl glycoside of N-acetylneuraminic acid with iluoroacetyl imidazole has afforded a mixture of 4,5-and 4,9-di-0-(fluoroacetyl) derivatives. A 4-acetamido-4-deoxy-4-epi-derivative of -acetylneuraminic acid has been prepared using standard techniques. ... 

In 1969, Schoop et aL found that pig submaxillary slices could synthesize NGN from acetate, N-acetylmannosamine, or N-acetylneu-raminic acid, all labeled in the acetate moiety. Schauer (1970a 1970Z ) demonstrated an enzyme system in high-speed supernatants of hog submaxillary gland extracts capable of oxidizing N-acetylneuraminic acid or A -acetylmannosamine to A/ -glycolylneuraminic acid. The enzyme is called N-acetylneuraminaterOg-oxidoreductase and requires O2 and ascorbate or NADPH for activity. It appeared that free N-acetylneuraminic acid is the substrate, but it is possible that CMP-NAN or the 9-phosphate ester is the substrate. 

A-Acetylneuraminic acid 4,7,8,9-Tetra-Ac, Me ester, A-20 A-Acetylneuraminic acid 4,7,8,9-Tetrabenzoyl, Me ester, A-20 A-Acetylneuraminic acid, A-20 6- O -(N-Acetyl-a-D-neuraminyl)-D-galactose, A-22 4-Amino-3,4-dideoxy-araZ)iwo-2-heptulosonic acid D-form 6-Phosphate, A-385... 

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