Modifications of Glycans and Glycoconjugates

Abstract

This chapter provides an overview of the occurrence, function, and biosynthesis of glycosylationally-modified carbohydrates that are modified by carboxylate, sulfate, and phosphate esters, by methylation, and by epimerization reactions. One of the simplest carbohydrate modifications is the epimerization of a single stereocenter in a sugar residue. Epimerizations may occur preglycosylationally at the level of the sugar nucleotide. Alternatively, epimerizations can occur after the synthesis of the glycan or glycoconjugate, as seen in the biosynthesis of certain polysaccharides that contain hexuronic acid residues. Epimerizations are involved in the biosynthesis of three major glycans: β-D-mann..