Cleavage of the (1 goes to 3)-2-acetamido-2-deoxy-beta-D-glucopyranosyl linkage present in keratan sulfate. The A and B isoenzymes of human liver hexosaminidase (EC 3.2.1.30).
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.
D000118:Acetylglucosaminidase / Q000302:isolation & purification / Q000378:metabolism*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000201:enzymology; D006025:Glycosaminoglycans; D006596:Hexosaminidases / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D007632:Keratan Sulfate; D008099:Liver / Q000201:enzymology*; D012867:Skin / Q000201:enzymology; D013379:Substrate Specificity; D013661:Tay-Sachs Disease / Q000201:enzymology
D006025:Glycosaminoglycans; D007527:Isoenzymes; D007632:Keratan Sulfate; D006596:Hexosaminidases; D000118:Acetylglucosaminidase