Cellular blood group substances. IV. Neutral fucoglycolipids having long, branched carbohydrate chains. H-Active and I-active glycosphingolipids of human erthyrocyte membranes

Abstract

H-Active ceramide heptasaccharide (H2-glycolipid) and ceramide decasaccharide (H3-glycolipid) were isolated from blood group O human erythrocyte membranes. Their structures have been determined by conventional methylation analysis, enzymatic degradation, and direct total mass spectrometry of the enzymatic degradation products after permethylation and reduction with sodium bis(2-methoxyethoxy)aluminum hydride. The branched sugar residue in the structure of H3-glycolipid was unambiguously determined by a new method with the combination of enzymatic degradation and comparison of the total mass spectrogram of the reduced product of the enzyme-degraded compounds. The proposed structures are as follows: (see article) The fourth component of H-active glycolipid (H4-glycolipid) was also isolated in chromatographically heterogenous form, but chemical analysis and methylation study indicate heterogeneity of the fraction. Both H3- and H4-glycolipids inhibit I-hemagglutination, whereas H1- and H2-glycolipids do not inhibit I-hemagglutination.