title: Residual mannosidase activity in human mannosidosis: characterization of the mutant enzyme.
abstract: The prenatal diagnosis of affected fetuses in two families at risk for mannosidosis gave us the opportunity to study the residual alpha-mannosidase activity. We found an altered acidic alpha-mannosidase characterized by lowered affinity toward the substrate, displacement of maximal activity toward pH 4-5, thermal lability, different migration in electrophoresis, and apparent change in molecular weight at alkaline pHs. The immunological properties seem unchanged since the enzyme was precipitated by an antiacidic alpha-mannosidase antiserum. The mutant enzyme instability, provoked by dialysis, and its reactivation after addition of dialysis fluid, suggests an association-dissociation phenomenon. We propose a possible hypothesis that a low molecular weight ligand is necessary to maintain the activity of the mutant enzyme.
mesh_terms: D002499:Centrifugation, Density Gradient; D004588:Electrophoresis, Cellulose Acetate; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008247:Lysosomes / Q000201:enzymology; D008361:Mannosidases / Q000172:deficiency* / Q000235:genetics; D009154:Mutation; D011247:Pregnancy; D011296:Prenatal Diagnosis
chemical_list: D008361:Mannosidases