Isolation and structural characterization of five major sialyloligosaccharides and a sialylglycopeptide from normal human urine.

Abstract

Five major sialyloligosaccharides and a sialylglycopeptide have been isolated from normal human urine by charcoal adsorption, gel filtration, ion-exchange chromatography, and paper chromatography. Structural studies including gas-liquid chromatography of monosaccharide and disaccharide derivatives, methylation analysis, glycosidase treatments, and CrO3 oxidation indicated the following structures for the compounds: 1, NeuAc(alpha 2-6)Gal(beta 1-4)Glc; 2, NeuAc(alpha 2-6)Gal(beta 1-4)GlcNAc; 3, NeuAc(alpha 2-3)Gal(beta 1-4)Glc; 4, NeuAc(alpha 2-3)Gal(beta 1-4) GlcNAc; 5, NeuAc(alpha 2-3)Gal(beta 1-3) [Neu-Ac(alpha 2-6)]GalNAc; and 6, NeuAc(alpha 2-3)Gal(beta 1-3) [NeuAc(alpha 2-6)]GalNAc (alpha 1-O)Ser. Compounds 4, 5, and 6 have not been described in a free form before. The presence of compound 5 in urine may suggest that it derives from glycoproteins through a catabolic pathway involving cleavage of the carbohydrate-peptide linkage by an endo-N-acetylgalactosaminidase. The predominating sialyloligosaccharides in urine were compounds 3 and 4. The predominance of the compounds with the sialyl(alpha 2-3) linkage is of interest in view of the recent discovery of uropathogenic Escherichia coli strains with binding specificity for sialyl(alpha 2-3)galactosides.