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

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, NcuAc(α2- 6)Gal(β1–4)GIe: 2. NeuAc(α2–6)Gal(β1–4)GIcNAc; 3. NeuAc(α2–3)Gal(β1–4)GIc; 4. NeuAc(α2–3)Gal(β1–4) GIcNAc: 5. NeuAc(α2–3)Gal(β1–3) [NeuAc(α2–6)]GalNAc; and 6. NeuAc(α2–3)Gal(β1–3) [NeuAc(α2–6)]GallNAc (α1-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(α2–3) linkage is of interest in view of the recent discovery of uropathogenic Escherchia coli strains with binding specificity for sialyl(α2–3)galactosides. [ABSTRACT FROM AUTHOR]