Structure of the Accumulating Oligosaccharide in Fucosidosis

Two water-soluble complex carbohydrate storage products were isolated from tissues and urine of patients with an inherited deficiency of lysosomal alpha-L-fucosidase (fucosidosis). The major component was an oligosaccharide of approximate molecular weight 1700, indicating that it was a dekasaccharide. From a combination of sequential digestion with purified exo-glycosidases, periodate oxidation and permethylation in conjunction with gas-liquid chromatography mass spectrometric analysis, the structure was found to be: Fuc(alpha 1 leads to 2)Gal-(beta 1 leads to 4) GlcNAc (beta1 leads to 2)Man [Fuc(alpha1 leads to 2) Gal (beta1 leads to 4) GlcNAc(beta1 leads to 2) Man] (alpha 1 leads to 3/6) Man (beta1 leads to 4) GlcNAc, although there was some evidence for heterogeneity at the mannose branchpoint. This material is structurally related to the stored oligosaccharides in patients with inherited deficiencies of beta-galactosidase (G M1-gangliosidosis) and N-acetyl-beta-hexosaminidase (G M2-gangliosidosis). A dissaccharide with the probable structure Fuc(alpha1 leads to 6)GlcNAc was found in lesser amounts in tissues; both are believed to be derived from the impaired catabolism of large numbers of different glycoproteins.