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), β-hexosaminidase (jack bean), and β-galactosidase. However, it could be degraded by a human liver β-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 β-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 G(D1a-GalNAc). The asialo derivative could then be degraded to GgOse₄-ceramide and GgOse₃-ceramide by sequential treatment with jack bean β-hexosaminidase and β-galactosidase. These data suggest that the novel ganglioside is a monosialosylpentahexosyl ceramide with the sialosyl group attached to the penultimate r224w1 =GalNAc(β1-4)Gal(β1-3)GalNAc(β1-4)Gal(β1-4)Glc-ceramide galactose moiety of the pentahexosyl ceramide backbone, and it has the following structure: (Ga1NAc(β1-4)Ga1(β1-3)Ga1NAc(β1-4)Ga1(β1-4)Glc-ceramide (3/2/α) NeuAc