title: Plasminogen activator inhibitor from human fibrosarcoma cells binds urokinase-type plasminogen activator, but not its proenzyme.
abstract: An approximately 75% pure form of a human Mr approximately 54,000 plasminogen activator inhibitor from conditioned culture fluid of the fibrosarcoma cell line HT-1080 was obtained by a single step of chromatography on concanavalin A-Sepharose. The inhibitor inhibited human urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator, but not plasmin. Rabbit antibodies against this plasminogen activator inhibitor also reacted with a plasminogen activator inhibitor with identical electrophoretic mobility in extracts of human blood platelets, indicating that the HT-1080-inhibitor is of the same type as the inhibitor of blood platelets. As revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by fibrin-agarose zymography, incubation of HT-1080-inhibitor with the active form of human u-PA led to the formation of an equimolar sodium dodecyl sulfate-resistant complex between them; in contrast, no complex formation was observed between the inhibitor and the proenzyme form of human u-PA (pro-u-PA). Likewise, using a column of anti-inhibitor antibodies coupled to Sepharose for removal of excess inhibitor and activator-inhibitor complexes, the potential enzymatic activity of pro-u-PA was found to be unaffected by incubation with inhibitor under conditions in which more than 95% of the active u-PA had formed complex with inhibitor.
mesh_terms: D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D004792:Enzyme Precursors / Q000037:antagonists & inhibitors*; D005337:Fibrin / Q000378:metabolism; D005354:Fibrosarcoma; D006023:Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007106:Immune Sera; D007457:Iodine Radioisotopes; D007700:Kinetics; D008970:Molecular Weight; D010960:Plasminogen Activators / Q000037:antagonists & inhibitors*; D015849:Plasminogen Inactivators; D013329:Structure-Activity Relationship; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors*
chemical_list: D004792:Enzyme Precursors; D006023:Glycoproteins; D007106:Immune Sera; D007457:Iodine Radioisotopes; D015849:Plasminogen Inactivators; D005337:Fibrin; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator