N-Acetylneuraminate synthase

Neu5Ac aldolase has also been used for the synthesis of 3-deoxy-D-mfl7j jo-octulosonic acid (KDO, 17) [16,17,20]. Condensation of o-arabinose (18) with pyruvate gave a mixture of KDO and 4-epi-KDO (19). Wong and coworkers have since reported the isolation of a KDO aldolase which produces KDO with complete stereospecificity at C-4 and also accepts a wide variety of carbohydrate substrates [51]. N-Acetylneuraminate synthase, found in Neisseria meningitidis, has been used to catalyse the condensation of 6-azido-6-deoxy-N-acetylmannosamine with phosphoenolpyruvate to give 9-azido-9-deoxy-Neu5Ac [52]. 

Synthetic studies for sialic acid and its modifications have extensively used the catabolic enzyme N-acetylneuraminic acid aldolase (NeuA E.C. 4.1.3.3), which catalyzes the reversible addition of pyruvate (70) to N-acetyl-D-mannosamine (ManNAc, 11) to form the parent sialic acid N-acetylneuraminic acid (NeuSNAc, 12 Scheme 2.2.5.23) [1, 2, 45]. In contrast, the N-acetylneuraminic acid synthase (NeuS E.C. 4.1.3.19) has practically been ignored, although it holds considerable synthetic potential in that the enzyme utilizes phosphoenolpyruvate (PEP, 71) as a preformed enol nucleophile from which release of inorganic phosphate during... 

The availability of both the cataboHc aldolase and the uniquely synthetic anabolic synthase made it possible to assemble a novel continuous assay for the determination of the metabolite N-acetylneuraminic acid [46]. A combination of both enzymes, in the presence of an excess of PEP, will start a cycle in which the determinant sialic acid will undergo a steady conversion of cleavage and re-syn-thesis as a futile cycle (Scheme 2.2.5.24). With each progression, however, 1 equiv of pyruvate is liberated simultaneously, which causes time-dependent signal amplification. Pyruvate is quantified spectrophotometrically by a corresponding NADH consumption when the system is coupled to the standard pyruvate dehy-... 

Preuss U, Gu X, Gu T, Yu RK. Purification and characterization of CMP-N-acetylneuraminic acid lactosylceramide (alpha 2-3) sialyltransferase (GM3-synthase) from rat brain. J. Biol. Chem. 1993 268 26273-26278. 

E. Schreiner, R. Christian, and E. Zribal, Synthesis of 9-deoxy-, 7,9-dideoxy-, and 4,7,9-trideoxy-N-acetylneuraminic acid and their behaviour towards CMP-sialate synthase, Liebigs Ann. Chem. p. 93 (1990). 

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-acetylneuraminate-9-phosphate synthase 4.1.3.20 ManNAc-6-P, PEP 7 — cytosol Watson etal. 1966... 

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. ... 

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