[51] Glycolipids

More than 50 different complete structures of glycosphingolipids (GSLs) of the ganglio, globo, and lacto families have been determined in the last three decades. Stepwise biosynthesis in vitro of about 20 GSLs, using membrane-bound or solubilized enzymes, has been reported. The short-chain glycosphingolipid substrates are amphiphilic molecules that aggregate in buffers at pH 6.0–8.0, whereas GSLs with long-chain carbohydrates tend to form micelles. Glycosphingolipids are thought to be packed tightly either in aggregates or in micelles, and thus are inaccessible to either membrane-bound or soluble glycosyltransferases (GLTs). This chapter reviews the structure, function, and biosynthesis of various GSLs. The chapter reviews the reports on glycosyltransferase reactions using specific glycosphingolipid acceptors. The assay systems of six families of GSL: GLTs and their merits are also described.