keratan-sulfate and Tay-Sachs-Disease

We have prepared a new substrate from a keratan sulfate-derived-oligosaccharide (2-acetamido-2-deoxyglucosyl-(1--3)-[1-3H] Galactitol), which is necessary to measure beta-N-acetylhexosaminidase activity. This substrate was prepared from a cornea keratan sulfate by digestion with endo-beta-galactosidase, followed by isolation of disaccharide on gel filtration chromatography and chemical desulfation. Using this substrate, we found that a striking deficiency of beta-N-acetylhexosaminidase activity was present in the skin fibroblasts of patients with Sandhoff disease but not in Tay-Sachs disease. Both beta-N-acetyl-hexosaminidase A & H contributed to the catabolism of keratan sulfate.

Topics: beta-N-Acetylhexosaminidases; Cells, Cultured; Chromatography, DEAE-Cellulose; Chromatography, Paper; Disaccharides; Fibroblasts; Glycosaminoglycans; Hexosaminidases; Humans; Keratan Sulfate; Sandhoff Disease; Tay-Sachs Disease

The disaccharide 2-acetamido-2-deoxy-beta-D-glucopyranosyl-(1 goes to 3)-D-[1-3H]-galactitol, prepared from keratan sulfate, was rapidly hydrolyzed by the A and B isoenzymes of normal human liver hexosaminidase (EC 3.2.1.30), and by the B isoenzyme prepared from the liver of a patient who had died of Tay-Sachs disease. The disaccharide substrate was also hydrolyzed by extracts of normal, cultured-skin fibroblasts, and fibroblasts of patients with Tay-Sachs disease, whereas it was not hydrolyzed by fibroblast extracts of patients with Sandhoff disease. Thus, effective degradation of keratan sulfate, secondary to a defect of the beta subunits present in the A and B isoenzymes of hexosaminidase, may contribute to the appearance of skeletal lesions in patients affected by Sandhoff disease.

Topics: Acetylglucosaminidase; Cells, Cultured; Fibroblasts; Glycosaminoglycans; Hexosaminidases; Humans; Isoenzymes; Keratan Sulfate; Liver; Skin; Substrate Specificity; Tay-Sachs Disease

Simple methods for the detection of keratan sulphate in urine have been applied to over 300 urine samples collected from children and adults with bone and cartilage dysplasias with or without mental retardation. Abnormal keratan sulphate excretion, which is a feature of type IV mucopolysaccharidosis (Morquio syndrome), is found in patients with that condition only during childhood. Abnormal excretion is also a feature of Kniest dysplasia and GM1 gangliosidosis and may be present in a number of other bone and cartilage dysplasias of unknown aetiology.

Topics: Adolescent; Adult; Bone Diseases; Child; Child, Preschool; Female; Glycosaminoglycans; Humans; Infant; Keratan Sulfate; Male; Middle Aged; Mucopolysaccharidosis IV; Tay-Sachs Disease