Isolation and characterization of a novel monosialosylpentahexosyl ceramide from Tay-Sachs brain.

A novel monosialoganglioside was isolated from Tay-Sachs brains. It represented about 0.1% of the total ganglioside mixture. Compositional analysis by gas-liquid chromatography indicated that it contained glucose, galactose, N-acetylgalactosamine, N-acetylneuraminic acid, and long chain base in the molar ratio of 1:2:2:1:1. The ganglioside was found to be resistant to neuraminidase (Clostridium perfringens), beta-hexosaminidase (jack bean), and beta-galactosidase. However, it could be degraded by a human liver beta-hexosaminidase preparation in the presence of an activator to produce a glycolipid chromatographically identical with authentic IV3NeuAc-GgOse4-ceramide. This glycolipid product was resistant to beta-galactosidase (jack bean), but could be readily degraded to GgOse4-ceramide by neuraminidase. Mild formic acid hydrolysis degraded the intact ganglioside to an asialo derivative chromatographically identical with the pentahexosyl ceramide (GalNAc-Gal-GalNAc-Gal-Glc-ceramide) derived from GD1a-GalNAc. The asialo derivative could then be degraded to GgOse4-ceramide and GgOse3-ceramide by sequential treatment with jack bean beta-hexosaminidase and beta-galactosidase. These data suggest that the novel ganglioside is a monosialosylpentahexosyl ceramide with the sialosyl group attached to the penultimate galactose moiety of the pentahexosyl ceramide backbone, and it has the following structure: GalNAc(beta 1-4)Gal(beta 1-3)GalNAc(beta 1-4)Gal(beta 1-4)Glc-ceramide (formula see text).