A Mannose-containing Trisaccharide Isolated from Urines of Three Patients with Mannosidosis

The urine from three patients with mannosidosis was found to contain abnormally high amounts of mannose-containing oligosaccharides. The highest yield (123 to 430 mg per liter of urine) was obtained of a trisaccharide, which was isolated and characterized. The isolation procedure included ultrafiltration, gel chromatography on Sephadex G-25, purification by preparative zone electrophoresis, and preparative paper chromatography. Sugar analysis showed that the trisaccharide consisted of 2 d-mannose moieties and 1 2-acetamido-2-deoxy-d-glucose residue. The linkages and sequential order of the sugar units were established by methylation analysis of the reduced trisaccharide. The partially methylated sugars obtained on hydrolysis of the methylated trisaccharide alditol were analyzed by gas-liquid chromatography and mass spectrometry. The anomeric configurations were determined by chromium trioxide oxidation followed by methylation analysis. Additional proof for the anomeric natures of the sugar units was obtained by enzymatic hydrolysis studies and by inhibition experiments using a precipitin system with concanavalin A. As a result of these studies, the structure of the trisaccharide could be established as α-d-mannopyranoside-(1→3)-β-d-mannopyranoside-(1→4)-2-acetamido-2-deoxy-d-glucose. The oligosaccharide is most probably a degradation product derived from the inner core of glycoprotein chains.