Identification and synthetic pathway of sialyl-Lewis x-containing neolacto-series gangliosides in lens tissues. 2. Enzymatic synthesis of sialyl-Lewis x gangliosides in monkey and rat lenses

Abstract

In Japanese monkey lenses, 3H-labeled fucose and N-acetylneuraminic acid were enzymatically transferred to neolactotetraosylceramide (nLc4) and III 3FucnLc4, respectively, suggesting the presence of a synthetic pathway of IV 3NeuACIII 3FucnLc4 via III 3FucnLc4 in monkey lenses. Six rat strains, Wistar, Sprague-Dawley and pigmented strains, contained sialyl-Lewis x gangliosides in non-cataractous lenses in a strain-specific manner. Glycosyltransferase assay revealed that the transfer of 3H-labeled fucose to nLc4 occurred in all the strains, but that the transfer of 3H-labeled N-acetylneuraminic acid to III 3FucnLc4 was strain-specific. These results suggested that sialyl-Lewis x gangliosides were generally synthesized from neolactotetraosylceramide via Lewis x glycolipid (III 3FucnLc4) in lens tissues, differing from other tissues. Combining our results, we propose two synthetic pathways of sialyl-Le x-containing neolacto-series gangliosides and A-pathway ganglio-series gangliosides in human senile cataractous lens: one to sialyl-Lewis x gangliosides from nLc4 via Lewis x glycolipid, and the other to GD1a from GM3, via GM2 and GM1.