Synthesis of fluorescent glycosphingolipids and neoglycoconjugates which contain 6-gala oligosaccharides using the transglycosylation reaction of a novel endoglycoceramidase (EGALC).

Endoglycoceramidase is a glycohydrolase capable of hydrolysing the O-glycosidic linkage between oligosaccharides and ceramides of various glycosphingolipids. However, no endoglycoceramidase reported so far can hydrolyse 6-gala series glycosphingolipids which possess the common structure R-Gal beta1-6Gal beta1-1'Cer. Recently, we found a novel endoglycoceramidase (endogalactosylceramidase, EGALC) which specifically hydrolyses 6-gala series glycosphingolipids. Here, we report that EGALC catalyses the hydrolysis as well as transglycosylation. An intact sugar chain of neogalatriaosylceramide (Gal beta1-6Gal beta1-6Gal beta1-1'Cer) was found to be transferred by EGALC to a primary hydroxyl group of various alkanols and non-ionic detergents such as Triton X-100 generating corresponding alkyl- and Triton-trigalactooligosaccharides. Furthermore, fluorescent 6-gala series glycosphingolipids were synthesized by transglycosylation in a reaction with EGALC using fluorescent ceramides as acceptors. Because of high efficiency and broad acceptor specificity, EGALC would facilitate the synthesis of fluorescent glycosphingolipids and neoglycoconjugates which contain 6-gala oligosaccharides.