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

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Abstract
Five major sialyloligosaccharides and a sialylglycopeptide were isolated from normal human urine by charcoal adsorption, gel filtration, ion-exchange chromatography and paper chromatography. Structural studies including GLC 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) [NeuAc(.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.

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