title: Kinetic analyses of the enhancement of the activities of t-PA induced by the presence of monoclonal antibody (C9-5).
abstract: Nine monoclonal antibodies (Mab) against two chain tissue plasminogen activator (t-PA(W] were obtained. The effects of these Mabs on the enzymatic activities of one chain t-PA (t-PA(TD] and two chain t-PA (t-PA(W] were examined by incubating t-PA and Mabs with S-2288, or with plasminogen (plg) and S-2251 in the presence or absence of fibrin. One of Mabs called C9-5 significantly enhanced the activities of t-PA, which were kinetically analyzed. The kinetic analyses of the hydrolysis of S-2288 by t-PA showed increase in kcat from 5.17/sec to 7.75/sec in the presence of 75 micrograms/ml of C9-5 without change in Km. When Glu-plg was activated by t-PA(TD) in the absence of fibrin, Km decreased from 2 microM to 0.17 microM in the presence of C9-5 without change in Vmax. The addition of fibrin resulted in further decrease in Km from 0.133 microM to 0.077 microM. When Lys-plg was activated by t-PA(TD) in the absence of fibrin, Km decreased from 0.408 microM to 0.185 microM in the presence of C9-5, and kcat increased from 0.131 sec-1 to 0.465 sec-1. The presence of fibrin further increased kcat of the activation of Lys-plg. Similar results were obtained when plasminogen was activated by t-PA(W). Mab, C9-5, was shown to bind to B-chain of t-PA by immunoblotting. These results suggest that a dimolecular complex of t-PA and C9-5 has a higher affinity to plasminogen in the presence or absence of fibrin.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D005340:Fibrinogen / Q000302:isolation & purification; D006801:Humans; D006868:Hydrolysis; D007120:Immunochemistry; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D009842:Oligopeptides / Q000378:metabolism; D013552:Swine; D013917:Thrombin / Q000302:isolation & purification; D010959:Tissue Plasminogen Activator / Q000276:immunology / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D009842:Oligopeptides; C018788:valyl-leucyl-lysine 4-nitroanilide; D005340:Fibrinogen; D013917:Thrombin; D010959:Tissue Plasminogen Activator