MULTIPLE CARBOHYDRATE-CLEAVING SPECIFICITIES IN HUMAN ACIDIC AND NEUTRAL GLYCOSIDASES

The common identity of human acidic β-d-glucosidase (β-d-glucoside glucohydrolase, EC 3.2.1.21) and β-d-xylosidase (1,4β-d-xylan xylohydrolase, EC 3.2.1.37) as one enzyme and that of acidic β-d-galactosidase (β-d-galactoside galactohydrolase, EC 3.2.1.23), β-d-fucosidase (no allotted EC number) and α-l-arabinosidase (α-l-arabinofuranoside arabinohydrolase, EC 3.2.1.55) as another enzyme is indicated by similar binding patterns of glycosidase activities of each enzyme to various lectins, by similar ratios between their intra- and extracellular levels in normal and I-cell fibroblasts and by their deficiencis in liver tissues from patients with Gaucher disease and GM1 gangliosidosis, respectively. A third enzyme, neutral β-d-galactosidase, purified to homogeneity from human liver has been shown to possess all these five glycosidase activities at neutral pH. These neutral enzymic activities were not bound by any of the lectins examined and found to be reduced in liver and spleen of a patient with neutral β-d-galactosidase deficiency. An additional form of β-d-xylosidase with optimal activity at pH 7.4 was bound by the fucose-binding lectin from Ulex eurpaeus while no binding was observed for the acidic (pH 4.8) and neutral (pH 7.0) β-d-xylosidase activities of the multiple glycosidase enzymes. © 1979.