ChemInform Abstract: Biosynthesis of Bacterial Polysaccharide Chains Composed of Repeating Units

Abstract

Publisher Summary This chapter describes the biosynthesis of bacterial polysaccharide chains composed of repeating units. A number of complicated polymers having chains composed of monosaccharide residues are present at the surface of bacterial cells. These polymers often serve as the characteristic antigens of bacteria and are very diverse in their structure. They may be divided into three main groups: (1) Cell-wall polymers that are characteristic mainly of Gram-positive bacteria, where different glycan chains are interconnected by covalent linkages, producing an enormous, cross-linked macromolecule. (2) Polymers having carbohydrate chains linked to a lipid anchor embedded in a bacterial membrane, termed as “bacterial amphiphiles,” and (3) Exocellular polysaccharides that are produced by the strains of both Gram-positive and Gram-negative bacteria. Monosaccharides are activated for participation in glycosylation reactions by conversion into diphosphoric or phosphoric ester derivatives. Glycosyl nucleotides constitute the main, activated form of monosaccharides for their incorporation into polysaccharide chains; this occurs through glycosylation reactions with release of nucleoside 5′-diphosphates or nucleoside 5′-phosphates. Polyprenyl glycosyl monophosphates have been shown to serve as glycosyl donors in the biosynthesis of side chains of some polysaccharides. The monosaccharide structures and the nature of their activated forms are also analyzed in the chapter.