Human hepatoma gangliosides: occurrence of a novel I-type glycolipid with NeuAc alpha 2-6Gal structure.

Gangliosides with NeuAc alpha 2-6Gal structure have been studied in human hepatocellular carcinoma. The gangliosides were purified to homogeneity by a DEAE-Sephadex A-25 column chromatography and by repeated silica beads column chromatography. Three gangliosides containing NeuAc alpha 2-6Gal structure were isolated and were structurally characterized by using monoclonal antibodies, proton nuclear magnetic resonance, fast atom bombardment mass spectrometry, methylation analysis by gas chromatography-mass spectrometry, and exoglycosidase treatments. The first compound was identified as NeuAc alpha 2-6Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1Cer. The structures of 2 other components were concluded to be as follows: [formula: see text] The first compound is a ganglioside that is characteristic of human meconium. The second compound has the same structure as a ganglioside recently found by us (Taki, T., Rokukawa, C., Kasama, T., Kon, K., Ando, S., Abe, T., and Handa, S., J. Biol. Chem., 267: 11811-11817, 1992) in meconium. The third compound is a novel type of ganglioside having blood group I-type structure as the core sequence. In addition to these gangliosides, 5 others were detected, and all except for GM3 were glycolipids with neolacto-series core structure. These results suggest that enzymes for the synthesis of neolacto type and NeuAc alpha 2-6Gal structure of glycolipids are activated in hepatoma.