Structural and immunological studies on a sialoglycopeptide isolated from human urine

Isolation of Unusually Composed Sialyl-Compounds from Hemofiltrate

Sialyl compounds are essential components of various biological fluids but relatively little is known about their occurrence in the extracellular fluid of patients with end-stage renal disease. As we have developed a macropreparative method for concentrating and desalting a wide range of fractions from diluted biological fluids we have been able to isolate and identify 5 sialooligosaccharides, 3 sialosugarphosphates, 2 monosialoglycopeptides and 1 disialoglycopeptide. The structures have been elucidated predominantly by one and two-dimensional NMR spectroscopy, enzymatic degradation and FAB mass spectrometry.

The accumulation of these compounds in uremic sera may be of particular interest as they may interact in the molecular biology of diseases typically associated with the uremic state, e.g., immune deficiency, neurological disorders, receptor binding abnormalities, complement system disturbances and cell membrane alterations.

The structure of sialyl-glycopeptides of the O-glycosidic type, isolated from sialidosis (mucolipidosis I) urine

Sialyl-glycopeptides containing an O-glycosidically linked tetrasaccharide chain were obtained from the urine of a patient suffering from mucolipidosis I. Isolation of these compounds was achieved by gel filtration, ion-exchange chromatography and preparative paper chromatography. Their structures were determined by a combination of carbohydrate and amino acid analysis, dansylation, periodate oxidation, methylation studies, enzymatic hydrolysis and 1H-NMR spectroscopy, to be as follows: (formula; see text) wherein R = peptide linked through -Thr-, -Ser-Thr- or -Thr-Ser-. The finding of these glycopeptides in urine shows that mucolipidosis I is characterized by a general "glycoprotein-specific" sialidase deficiency. The possibility of the existence of a human endo-alpha-N-acetylgalactosaminidase is discussed.

Isolation and characteristics of human urinary sialoglycoproteins

Three sialoglycoproteins (S1, S2, and S3) have been isolated from normal human urine by ultrafiltration, zone electrophoresis, gel chromatography, and ion-exchange chromatography. The average yields per litre of urine were 0.39 mg (S1), 0.40 mg (S2), and 1.9 mg (S3). The isolated substances were homogeneous on ultracentrifugation both at neutral and acid pH with sedimentation coefficients of 3.6 S (S1), 2.4S (S2), and 0.93S (S3). Equilibrium ultracentrifugation gave molecular weights of 77900 (S1), 37000 (S2), and 5300 (S3). All three components were rich in carbohydrate (64 to 76%) and contained 28 to 35% of sialic acid. Alkaline borohydride degradation of component S3 yielded two sialylated oligosaccharides which were partially characterized. The origin of the isolated substances is unknown. The molecular size of S3 (Stokes' radius of 2.0 nm) is compatible with passage from the blood by glomerular filtration whereas the size of S1 (Stokes' radius of 6.5 nm) would suggest a renal origin.

Isolation of acidic glycopeptides from urine by means of anion-exchange resins. Application to some cases of glycosphingolipidosis or mucolipidosis

An acidic fraction containing aminosugar was isolated by means of Dowex 1 from normal human urine which had previously been filtered through Ecteolacellulose. After purification, the fraction was shown to be composed of peptides and carbohydrates in comparable amounts. Threonine, serine and dicarboxylic acids were the principal amino acids. The carbohydrate moiety was mainly composed of galactose and glucosamine in the approximate ratio 3 : 1, together with smaller amounts of fucose, sialic acid, galactosamine and mannose. The presence of an O-glycosidic bond to threonine was shown by alkali treatment in reducing conditions. The fraction is probably a mixture of acidic glycopeptides. Fractions showing similar characteristics were isolated from urine of patients with Niemann-Pick disease, Gaucher's disease, I-cell disease, Ehlers-Danlos syndrome. Slight differences from the normal were found in the composition of the fraction isolated from GM1-gangliosidosis type 1.