N-acetylneuraminic acid aldolase

Extensive studies have indicated that only pyruvate is acceptable as the NeuA donor substrate, with the exception of fluoropyruvate [49], but that the enzyme displays a fairly broad tolerance for stereochemically related aldehyde substrates as acceptor alternatives, such as a number of sugars and their derivatives larger or equal to pentoses [36,48,50,51]. Permissible variations include replacement of the natural D-manno configured substrate (4) with derivatives containing modifications such as epimerization, substitution, or deletion at positions C-2, -4, or -6 [16,27]. Epimeriza-tion at C-2, however, is restricted to small polar substituents owing to strongly 

N-Acetylneuraminic acid aldolase (or sialic acid aldolase, NeuA EC 4.1.3.3) catalyzes the reversible addition of pyruvate (2) to N-acetyl-o-mannosamine 

Extensive studies have indicated that only pyruvate is acceptable as the NeuA donor substrate, with the exception of fiuoropyruvate [82], but that the enzyme has fairly broad tolerance of stereochemically related aldehyde 

Industrial process for the production of N-acetyIneuraminic acid as a precursor to an influenza inhibitor. 

Neuraminic acid derivatives accessible by NeuA catalysis. 

Sugar derivatives not accepted by NeuA in direction of synthesis or cleavage, and use of fluoropyruvate for synthesis of fluorosialates. 

N-Acetylneuraminic acid aldolase (Neu catalyzed synthesis of sialic acid (4) and deoxy-D-glycero-D-galacto-2-nonuio-sonic acid (KDN, 5) through aldol addition of pyruvate to N-acetyl-D-mannosamine (2) and D-manose (3). 

Examples of structurally diverse sialic acid, o-ManNAc and o-mannose derivatives synthesized using NeuA. 

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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]. 

Figure 6. Synthesis of 9-0-acetyl-N-acetylneuraminic acid. The aldol acceptor was prepared from N-acetylmannosamine and isopropenyl acetate in DMF catalyzed by protease N obtained from Amano. The aldol condensation was carried out by using N-acetylneuraminic acid aldolase as catalyst.

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... 

In considering the application of enzyme catalysis to DCC, we were encouraged by the thermodynamic resolution of a dynamic mixture of aldol products by Whitesides and co-workers through the use of a broad-specificity aldolase to lead to reversible formation of carbon-carbon bonds under mild conditions.35 For the current investigation36 we chose a related enzyme, N-acetylneuraminic acid aldolase (NANA aldolase, EC 4.1.3.3), which catalyzes the cleavage of N-acetylneuraminic acid (sialic acid, 27a) to A-acetylmannosamine (ManNAc, 28a), and sodium pyruvate 29 in the presence of excess sodium pyruvate, aldol products 27a-c are generated from... 

N-Acetylneuraminic acid aldolase (NeuAc aldolase) is commercially available and has been the subject of much attention [49]. NeuAc aldolase catalyzes the aldol reaction between pyruvate and mannose or mannose derivatives. The enzyme activates the donor as its enamine, similar to the Type I aldolase described above (Scheme 5.21). The enzyme has been used for the synthesis of aza sugars and var-... 

In a related protocol, the acetaldehyde trimer 54 from the generic RibA oligomerization was found to be a substrate for the N-acetylneuraminic acid aldolase (NeuA EC 4.1.3.3) which catalyzed the addition of pyruvate. By this means, a tetradeoxy-L-arahi o-2-nonulosonic acid 56 was obtained in 55% yield [116]. A one-pot, tandem operation was complicated by the fact that temperature requirements for optimum activity and stability of the two catalysts were not compatible. 

N-Acetylneuraminic Acid Aldolase (Sialic acid aldolase, EC 4.1.33)... 

N-Acetylneuraminic acid aldolase, use in fluorinated sugar synthesis, 158,161/ Acylation-hydrolysis of ylides, 2-fluoro-2-oxoalkanoate synthesis, 96-100 Acyl hypofluorites applications, 58 applications for shorter chain homologues, 60,61/ chemistry, 58—61... 

N-Acetylneuraminic acid aldolase catalyzes the cleavage of N-acetylneuraminic acid (Neu5Ac) to N-acetylmannosamine (ManNAc) and pyruvate (Pyr). The reverse reaction can be employed to synthesize N-acetylneuraminic acid, which plays an important physiological role as a terminal sugar residue of glycosylated proteins 1481 (Eq. (3)). 

N-Acetylneuraminic acid aldolase catalyzes the reversible aldol condensation of pyruvate (23) and N-acetylmannosamine (22 ManNAc) to form N-acetylneuraminic acid (24 NeuAc N-acetyl-5-amino-3,5-dideoxy-D-glycerogalacto-2-nonulopyronic acid Scheme 6).80-83 In vivo the enzyme has a catabolic function and the equilibrium for this reaction is near unity the presence of excess pyruvate can shift this equilibrium. NeuAc and other derivatives of neuraminic acid are termed sialic acids. These compounds are found at the termini of mammalian glycoconjugates and play an important role in cellular recognition.84-89 The production of analogs of NeuAc is a point of great interest to synthetic and medicinal chemists. The enzymatic approach has not been fully explored but it may be a practical alternative to the chemical synthesis of certain sialic acids.89... 

W. Fitz, J.-R. Schwark, C.-H. Wong, Aldotetroses and C(3)-modified aldohexoses as substrates for N-acetylneuraminic acid aldolase a model for the explanation of the normal and the inversed stereoselectivity, J. Oig. Chem. 60 (1995) 3663-3670. 

Kiefel, M. J., Wilson, J. C., Bennett, S., Gredley, M., and von Itzstein, M., Synthesis and evaluation of C-9 modified N-acetylneuraminic acid derivatives as substrates for N-acetylneuraminic acid aldolase. Bioorg. Med. Chem. 2000,8 (3), 657-664. 

Comb, D. G., and Roseman, S., 1962, N-acetylneuraminic acid aldolase. Methods Enzymol. 5 391. 

Gantt, R., Millner, S., and Binkley, S. B., 1964, Inhibition of N-acetylneuraminic acid aldolase by 3-fluorosialic acid. Biochemistry 3 1952. 

Figure 4 Natural substrates of the N-acetylneuraminic acid aldolase.

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