9-0-Acetylated sialic acids, recognition

Acetylation and A -acetyl-hydroxylation are modifications of sialic acids that are known to have an antirecognition effect on the binding of influenza A and B viruses (Higa et al., 1985 Section 4.1). This is in contrast to the specific recognition of 9-O-acetylated sialic acids by influenza C virus (Rogers et al., 1986 see Section 4.1 and Chapter 9). 

Harms, G., Corfield, A. P., Schauer, R., and Reuter, G., 1993, Recognition of 0-acetylated sialic acids by influenza C virus, Biol. Chem. Hoppe-Seyler 374 946-947. 

Mucin-type O-linked glycans are decorated with a variety of capping structures. Given their prominent location, these structures play critical roles in cell-cell and cell-matrix recognition events. The most common modifications are fucosylation, sia-lylation, and sulfation. Terminal sialic acids can also be further modified by O-acetylation at the 7 or 9 position. 

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... 

A-acetyl neuraminic acid lyase (NAL) catalyzes the reversible aldol addition of N-acetylmannosamine to pyruvate to produce A-acetylneuraminic acid, a sialic acid. Sialic acid is an essential component of complex carbohydrates which are of paramount importance as recognition signals in a variety of biological process, such as parasite invasion, infectivity and survival of the invading organism in the host. Hence, sialic acids mimetics, such as the commercial Oseltamavir, Relenza and... 

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