A new glycolipid antigen isolated from human erythrocyte membranes reacting with antibodies directed to globo-N-tetraosylceramide (globoside).

Two glycolipid fractions were separated by high performance liquid chromatography from human erythrocyte membranes and which were reactive with antibodies to globo-N-tetraosylceramide (globoside). The reactivity to the antibody was abolished by treatment with endo-beta-galactosidase of Escherichia freundii which specifically hydrolyzes lacto-N-glycosyl series glycolipids, but does not hydrolyze globo series glycolipids. One of the fractions was isolated by repeated high performance liquid chromatography, and its structure was determined by direct probe mass spectrometry, methylation analysis, and by degradation with exo- and endoglycosidases as follows: GalNAc beta 1 leads to 3Gal beta 1 leads to 4GLcNAc beta 1 leads to 3 Gal beta 1 leads to 4Glc beta 1 leads to 1ceramide. The carbohydrate structure was identical with the asialo core of "G3-ganglioside" (IV3NeuAc2 leads to 3GalNAcLcnOs4Cer) (Watanabe, K., and Hakomori, S. (1979) Biochemistry 14,5502-5504), but the ceramide moiety of this glycolipid was characterized by having C22 and C24 fatty acids in a striking contrast to that G3-ganglioside was characterized by the predominance of C14 fatty acid. Since globoside was previously identified as blood group P antigen (Marcus, D. M., Kundu, S. K., and Suzuki, A. (1981) Semin. Hematol. 18, 63-71), and both globoside and this glycolipid possess the common terminal structure GalNAc beta 1 leads to 3Gal, this glycolipid may represent the second blood group P antigen belonging to the lacto series.