Isolation and partial characterization of blood group A and H active glycosphingolipids of rat small intestine.

Blood group A and H active glycosphingolipids have been isolated from rat small intestine. By mass spectrometry of the permethylated and LiAlH4-reduced permethylated glycolipid derivatives, the A glycolipids were shown to contain four (A-4), six (A-6), and 12 (A-12) sugar residues, respectively. The anomeric structure of the A-4 and A-6 glycolipids was established by proton NMR spectroscopy of the permethylated-reduced derivatives. Acid degradation and gas chromatography were used for analysis of binding positions. The structures of the A-4 and A-6 glycolipids were GalNAcp alpha 1 leads to 3Galp(2 comes from 1Fucp alpha) beta 1 leads to Glcp beta 1 leads to 1Cer and GalNAcp alpha 1 leads to 3Galp(2 comes from 1Fucp alpha) beta 1 leads to 3GlcNAcp beta 1 leads to 4Galp beta 1 leads to 4Glcp beta 1 leads to 1Cer. The third glycolipid (A-12) was a branched dodecaglycosylceramide with two blood group A determinants. The complete structure of this glycolipid has not yet been solved. The blood group A activity was the same for the A-6 and A-12 glycolipids based on an equal number of blood group A determinants, but the activity of the A-4 compound was only about half of the others. The A-6 glycolipid was based on a type 1 (Gal beta 1 leads to 3GlcNAc) carbohydrate chain, thus differing from the already known isomer based on a type 2 chain (Gal beta 1 leads to 4GlcNAc) present in human erythrocyte. The blood group A activity of these two glycolipids was found to be identical. The three rat intestinal blood group A active glycolipids were exclusively located to the mucosa epithelial cells. The blood group H active tri- and pentaglycosylceramides (H-3 and H-5), presumed to be the precursors of the A-4 and A-6 glycolipids, were also identified. A 10-sugar glycolipid (H-10), a possible precursor of A-12, was not detected.