53] Sialic ACIDS: Metabolism of O-acetyl groups

Abstract

O -Acetylated sialic acids are often components of oligosaccharides or polysaccharides, glycoproteins, and gangliosides from microorganisms, animals, and humans. The chapter presents a list of 18 known natural O -acetylated sialic acids in a tabular form. Sialic acid O -acetyl groups may influence the conformation and arrangement of glycoconjugates in cell membranes, as these ester groups have been shown to modify hydrogen bonding in sialic acids. They may also reduce the hydrophilic properties of sialic acids. The most important general role of O -acetyl groups in sialic acids is to retard the degradation of glycoconjugates. This chapter describes the metabolism of sialic acids in detail. There is also a description of three systems that are involved in the metabolism of these sialic acids. Those systems are O -acetyltransferases, esterase, and nonenzymatic O-acetyl migration. The discovery of the esterase exhibiting preferred hydrolysis of sialic acid O-acetyl groups contributes much to the understanding of the metabolism of sialic acids. The enzyme is believed to be involved in the regulation of the catabolic site of this metabolism, by assisting the action of sialidases on O -acetylated sialic acids. It participates in the regulation of the biological functions of O -acetyl groups of sialic acids.