Sialyltransferase Activity Assay for Ganglioside GM3 Synthase.

GM3 synthase (GM3S) is a sialyltransferase that transfers sialic acid from CMP-sialic acid to lactosylceramide. This reaction results in formation of ganglioside GM3 and is essential for biosynthesis of its downstream derivatives, which include a- and b-series gangliosides. Here, we describe a method for GM3S enzymatic assay using fluorescence-labeled alkyl lactoside as acceptor substrate, followed by HPLC for separation of enzymatic product. The method allows quantitative assay of GM3S sialyltransferase activity in cultured cells and mouse brain tissues.