Activation of human beta-glucuronidase by murine monoclonal antibodies and bovine serum albumin in an uncompetitive fashion.
Catalytic antiidiotypic antibodies exhibit enzyme activity because they possess the internal image of the enzyme that serves as the antigen. However, we have found that non-catalytic monoclonal antibodies specific for human beta-glucuronidase and, to a lesser extent, bovine serum albumin were capable of enhancing the activity of this enzyme. The stability of the enzyme was not increased by these proteins. Enzyme kinetic studies revealed an uncompetitive activation mechanism with a proportional increase in both maximal velocity and Michaelis constant of the enzyme with the increase in the protein concentration. These three proteins apparently bound to the enzyme with subsequent alteration of its affinity for the substrate. Activation of the enzyme by its non-catalytic antibody might not be a rare occurrence and it could play a pathogenic role in certain disease processes.
Department of Pathology, University of Alabama at Birmingham 35233, USA.
K J
KJ
Ho
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D002417:Cattle; D002846:Chromatography, Affinity; D004789:Enzyme Activation; D005966:Glucuronidase / Q000302:isolation & purification / Q000378:metabolism*; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008433:Mathematics; D051379:Mice; D008807:Mice, Inbred BALB C / Q000276:immunology; D008962:Models, Theoretical; D012710:Serum Albumin, Bovine / Q000494:pharmacology*
D000911:Antibodies, Monoclonal; D006146:Guanidines; D007074:Immunoglobulin G; D012710:Serum Albumin, Bovine; D005966:Glucuronidase; D019791:Guanidine