Role and metabolism of glycoconjugate sulfation

Membranes of many cell types or cell secretions contain sulfated glycoconjugates with a variety of different structures. The sulfate groups are terminal structures on oligosaccharides and may endow these molecules with special biological effects. Sulfates may mask antigenic or lectin binding sites, they may protect physiologically important compounds from premature degradation, or they may regulate the biosynthesis and biological role of glycoproteins and proteoglycans. Sulfate has been suggested to be heavily involved in binding events which influence diverse functions, such as root nodulation in legumes, lymphocyte homing, cell-cell adhesion and viral replication. Many different sulfotransferases exist in nature; these enzymes synthesize various sulfate esters with great specificity, similar to that of glycosyltransferases. A better understanding of the role of sulfation will follow upon further characterization and cloning of sulfotransferases, together with studies which define their regulation and gene expression.