Cell-specific differences in membrane beta-glucosidase from normal and Gaucher cells.
Two isozymes of membrane-bound beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) with activity towards 4-methylumbelliferyl-beta-D-glucopyranoside have been identified in human cells. One of these isozymes was found to have a pH optimum of 5.0, a Km of 0.4 mM and to be rapidly inactivated at pH 4.0 ("acid-labile"). The second isozyme had a pH optimum of 4.5, a Km of 0.8 mM and was stable at pH 4.0 ("acid-stable"). Cultured long-term lymphoid lines and peripheral blood leukocytes contained both isozymes while cultured skin fibroblasts contained only the "acid-stable" form in detectable amounts. The specific activity of the "acid-stable" isozyme was severely reduced in cultured skin fibroblasts, cultured long-term lines and peripheral leukocytes from patients with Gaucher's disease. The specific activity of the "acid-labile" enzyme in the latter two cell types was apparently unaffected. The beta-glucosidase activity in all three cell types examined was predominantly particulate but the enzyme could be solubilized with low concentrations of Triton X-100. The solubilized enzyme required sodium taurocholate (0.2%) for maximum activity. Solubilized beta-glucosidase did not exhibit the cell-specific differences in pH optimum and Km shown by the membrane-bound enzyme.
D002462:Cell Membrane / Q000201:enzymology*; D005347:Fibroblasts / Q000201:enzymology; D005776:Gaucher Disease / Q000201:enzymology*; D005959:Glucosidases / Q000378:metabolism*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D007962:Leukocytes / Q000201:enzymology; D008196:Lymph / Q000201:enzymology; D011092:Polyethylene Glycols / Q000494:pharmacology; D013656:Taurocholic Acid / Q000494:pharmacology
D007527:Isoenzymes; D011092:Polyethylene Glycols; D013656:Taurocholic Acid; D005959:Glucosidases