Substrate specificities of a bacterial sialidase and rat liver ganglioside GM3 sialyltransferase

Abstract

Sialidases cleave off sialic acid residues from the oligosaccharide chain of gangliosides in their catabolic pathway while sialyltransferases transfer sialic acid to the growing oligosaccharide moiety in ganglioside biosynthesis. Ganglioside GM3 is a common substrate for both types of enzymes, for sialidase acting on ganglioside GM3 as well as for ganglioside GD3 synthase. Therefore, it is possible that both enzymes recognize similar structural features of the sialic acid moiety of their common substrate, ganglioside GM3. Based on this idea we used a variety of GM3 derivatives as glycolipid substrates for a bacterial sialidase (Clostridium perfringens) and for GD3 synthase (of rat liver Golgi vesicles). This study revealed that those GM3 derivatives that were poorly degraded by sialidase also were hardly recognized by sialyltransferase (GD3 synthase). This may indicate similarities in the substrate binding sites of these enzymes.