A-acetylneuraminic

Commercial A -acetylneuraminic acid aldolase from Clostridium perfringens (NeuAcA EC 4.1.3.3) catalyzes the addition of pyruvate to A-acetyl-D-mannosamine. A number of sialic acid related carbohydrates are obtained with the natural substrate22"24 or via replacement by aldose derivatives containing modifications at positions C-2, -4, or -6 (Table 4)22,23,25 26. Generally, a high level of asymmetric induction is retained, with the exception of D-arabinose (epimeric at C-3) where stereorandom product formation occurs 25 2t The unfavorable equilibrium constant requires that the reaction must be driven forward by using an excess of one of the components in order to achieve satisfactory conversion (preferably 7-10 equivalents of pyruvate, for economic reasons). 

Nohle U, Beau JM, Schauer R (1982) Uptake, metabolism and excretion of orally and intravenously administered, double-labeled A-glycoloylneuraminic acid and single-labeled 2-deoxy-2,3-dehydro-A-acetylneuraminic acid in mouse and rat, Eur J Biochem 126 543-548 Oxford J (2005) Oseltamivir in the management of influenza. Expert Opin Pharmacother 6 2493-2500... 

Mahmoudian, M., Noble, D., Drake, C.S., Middleton, R.F., Montgomery, D.S., Piercey, J.E., Ramlakhan, D., Todd, M. and Dawson, M.J., An efficient process for production of A-acetylneuraminic acid using A-acetylneuraminic acid aldolase. Enzyme Microb. Technol. 1997, 20, 393 00. 

Cytidine 5 -phospho-A-acetylneuraminate (298), the coenzyme of sialyltransferases, is a sugar-nucleotide in which the leaving group is a nucleotidyl monophosphate that contains a carboxylate group directly attached to the anomeric centre. Studies of its hydrolysis reveal that at pH 5 specific acid catalysis occurs (Scheme 34) to yield a glycosyl carbocation as a tight ion pair, the lifetime of which was estimated... 

Scheme 2.7 Aldol reaction of ManNAc analogues and sodium pyruvate to produce sialic acid, catalyzed by A-acetylneuraminic acid (NANA) aldolase.

Total Synthesis of the Biologically Active Form of A -Acetylneuraminic Acid... 

This enzyme [EC 4.1.3.3], also known as A-acetylneu-raminate aldolase, will convert A-acetylneuraminate to A-acetylmannosamine and pyruvate. The enzyme will also act on A-glycoloylneuraminate and on O-acetylated sialic acids, other than O -acetylated derivatives. 

This enzyme [EC 2.7.7.43], also referred to as CMP-A-acetylneuraminic acid synthetase and CMP-sialate synthase, catalyzes the conversion of CTP and A-acylneu-raminate to yield pyrophosphate and CMP-A-acylneu-raminate. The protein will act on both the A-acetyl and A-glycolyl 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). 

Sialic acid aldolase (SA EC 4.1.3.3), also named A-acetylneuraminate pyruvate lyase, has been extensively used by our group in its immobilized form, first for the synthesis of large amounts of A-acety lneuraminic acid [20] and then for many natural and unnatural sialic acids [21], SA catalyzes the reversible aldol reaction of A-acetylmannosamine and pyruvate to give A-acety lneuraminic acid with an optimum pH for activity of 7.5 and an equilibrium constant of 12.7 A/-1 in the synthetic direction (Scheme 3) [10],... 

R. L. Halcomb, W. Fitz, and C.-H. Wong, Enzymatic synthesis of 7-deoxy-A/-acetylneuraminic acid and 7-O-methyl-N-acetylneuraminic acid, Tetrahedron Asymm. 5 2437 (1994). 

A-Acetylneuraminic acid A-Glycolylneuraminic acid A-Acetyl-O-acetyl-neuraminic acid... 

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