Understanding the Chemistry and Biology of Glycosylation with Glycan Synthesis.

Glycoscience research has been significantly impeded by the complex compositions of the glycans present in biological molecules and the lack of convenient tools suitable for studying the glycosylation process and its function. Polysaccharides and glycoconjugates are not encoded directly by genes; instead, their biosynthesis relies on the differential expression of carbohydrate enzymes, resulting in heterogeneous mixtures of glycoforms, each with a distinct physiological activity. Access to well-defined structures is required for functional study, and this has been provided by chemical and enzymatic synthesis and by the engineering of glycosylation pathways. This review covers general methods for preparing glycans commonly found in mammalian systems and applying them to the synthesis of therapeutically significant glycoconjugates (glycosaminoglycans, glycoproteins, glycolipids, glycosylphosphatidylinositol-anchored proteins) and the development of carbohydrate-based vaccines.