Anomeric Structures of Globoside and Ceramide Trihexoside of Human Erythrocytes and Hamster Fibroblasts

Characterization of B and H blood-group active glycosphingolopids from human B erythrocyte membranes

Two blood group B active glycosphingolipids (B-I and B-II) previously isolated and highly purified from human B erythrocytes [21] were analysed first by degradation with alpha-D-galactosidase from coffee beans, alpha-L-fucosidase from bovine kidney and with 0,1 N trichloracetic acid; the native B-glycolipids as well as their degradation products were then investigated by methylation analysis with combined gas chromatography-mass spectromety, by thin layer chromatography, two dimensional immunodiffusion and by the hemagglutination inhibition technique. Together with the results obtained by mass spectrometry of permethylated glycolipids [26] the following structures were elucidated: alpha-D-gakactpurampsu;-(1 leads to 3) [alpha-L-fucopyranosyl-(1 leads to 2)]-D-galactopyranosyl-(1 leads to 4)-N-acetyl-D-glucosaminosyl-(1 leads to 3)-D-galactopyranosyl-(1 leads to 4)-D-glucopyranosyl-(1 leads to 1)-ceramide for the B-I glycosphingolipid and alpha-D-galactopyransosyl-(1 leads to 3)-[alpha-L-fucopyranosyl-(1 leads to 2)]-D-galactopyranosyl-(1 leads to 4)-N-acetyl-D-glucosaminosyl-(1 leads to 3)-D-galactopyranosyl-(1 leads to 4)-N-acetyl-D-glucosaminosyl-(1 leads to 3)-D-galactopyranosyl-(1 leads to 4)-D-glucopyranosyl-(1 leads to 1)-ceramide for the B-II glycophingolipid. AH active glycolipid fraction from B erythrocytes further purified by thin layer chromatography was also investigated by methylation analysis. The pattern of its partially methylated alditol acetates was essentially the same as that of the alpha-galactosidase treated and permethylated B-I glycoliped. It is also exhibited strongly precipitating and hemagglutination inhibiting H properties as well as the two alpha-galactosidase treated B-I and B-II glycosphingolipids. Based upon these data the following tentative structure was proposed: alpha-L-fucopyranosyl-(1 leads to 2)-D-galactopyranosyl-(1 leads to 4)-N-acetyl-D-glucosaminosyl-(1 leads to 3)-D-Galactopyranosyl-(1 leads to 4)-D-glucopyranosyl-( 1 leads to 1)-ceramide. Gas chromatographic analysis revealed sphingosine and lignoceric, nervonic and behenic acids to be the main components of the ceramide residues of the three glycophingolipids. From the data presented the H active substance very probably can be regarded as the immediate precursor of the B-I gly cosphingolipid from human B erythrocyte membranes.

Biosynthesis of glycosyldiglycerides in Mycobacterium smegmatis

A particulate enzyme preparation from Mycobacterium smegmatis catalyzes the transfer of [(14)C]galactose from uridine 5'-diphosphate (UDP)-[(14)C]galactose and of [(14)C]glucose from UDP-[(14)C]glucose into chloroform-soluble products. The radioactive neutral lipids were purified by passage through diethylaminoethyl-cellulose, followed by thin-layer chromatography. When UDP-glucose was used as substrate, two major radioactive lipids were obtained; one had a hexose-glucose-glycerol ratio of 1:1:1. The second product had a hexose-glycerol ratio of 2:1 and, in addition to glucose, contained lesser amounts of mannose and galactose. With UDP-galactose as substrate, two radioactive products were observed that were chromatographically indistinguishable from the [(14)C]glucosyl-labeled mono- and diglycosyldiglyceride. Palmitate and oleate were the predominant fatty acid constituents in these lipids and were present in equimolar amounts in all of the products examined. The products have thus been identified as monoglycosyldiglyceride and a diglycosyldiglyceride containing glucose as the major hexose along with mannose and galactose. Properties of the galactosyl and glucosyl transferases are described.

Tissue receptor for cholera exotoxin: postulated structure from studies with GM1 ganglioside and related glycolipids

By a double-diffusion precipitation-in-gel technique, isolated cholera toxin as well as its natural toxoid were shown to be fixed and precipitated by the ganglioside G(M1) but not by any of the related glycolipids G(M3), G(M2), G(M1)-GlcNAc, G(D1a), G(D1b), G(T1), globoside, G(A1), and tetrahexoside-GlcNAc. Twenty-five nanograms of G(M1) was enough to give a precipitation line with 1.2 mug of toxin, whereas about 50 ng was required with this amount of toxoid. G(M1) also inactivated the toxin in the ileal loop as well as in the intradermal models in rabbits. A 1: 1 molar ratio of ganglioside to toxin was found limiting, e.g., 100 pg of G(M1) could inactivate 5 ng (about 50 blueing doses) of isolated toxin. G(M1) inactivated crude toxin (culture fil rate) with the same efficiency as isolated toxin, and the inactivating capacity of G(M1) was unaffected by mixing with other gangliosides, indicating the specificity in the reaction between G(M1) and toxin. The other glycolipids tested did not inactivate toxin except G(D1a) and G(A1) which did so with approximately 1,000 times less efficiency than G(M1). This identified the portion Gal --> GalNAc [Formula: see text] as the critical region in G(M1) for toxin fixation, and it is postulated that this may be the tissue receptor structure for the cholera toxin.