Abstract
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.
Highlights
Blood group A andH active glycosphingolipids have paper, we describe the isolation and structural characterizabeen isolated from rat small intestine
Structural Characterization of the A-12 Glycolipid-The total non-acid glycolipid fraction (Fig. 1,lane T) contained a major slow moving compound which wasisolated pure.Mass spectrometry of the intact glycolipid showedit to be a branched dodecaglycosylceramide with two blood group A determinants [26].The branching point was located on the fourth sugar residue from ceramide and type 1
Structural Characterization of the Blood Group H Type Precursors of the Blood Group A Glycolipids-The blood group A glycolipids presented here are probably synthesized by enzymatic addition of the terminal GalNAc to the correspondingblood groupH precursors [27,28].In a recenpt aper, we described the presence of a blood group H active triglycosylceramide (H-3) isolated from the black-white rat small intestine [29]
Summary
The total non-acid glycolipid fraction isolated from blackwhite rat small intestine is shown in Fig. 1, lane T.All bands glycolipids altogether (120 animals). In addition to the A-4 glycolipid, small amounts of a contaminating trihexosylceramidewere seen in the mass spectra This was best evident in the reduced spectrum where the peaks at m / e 924(16:O fatty acid),980 [200], lo08 [220], and 1036 (24:O)were due to threehexoses and the fattyacid which is similar tothe series at m / e 1125 to 1237 for the A-4 glycolipid. The reduction introduces a change of the chemical shift for some signals [24].The anomeric region of the NMR spectrum of the permethylated-reduced A-4 glycolipid is reproduced in Fig. 6,spectrum A This spectrum showed a sharp signal of Fuc at 5.32 ppm (J1,=2 3.4 Hz) due to an a proton.
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