title: Protease-nexin: a cellular component that links thrombin and plasminogen activator and mediates their binding to cells.
abstract: This report identifies a component of normal human fibroblasts that forms a covalent linkage with thrombin and urokinase (urinary plasmingoen activator) and mediates most of the specific cellular binding of these proteases. This component, here named protease-nexin (PN), is both associated with the cell surface and released into the culture medium. In several ways PN resembles antithrombin III (AT3), a prominent inhibitor of thrombin in serum: PN links thrombin, probably via an ester bond; PN does not link thrombin blocked at its catalytic site serine; PN has a high-affinity heparin-binding site; and heparin greatly accelerates the rate of linkage between soluble PN and thrombin. Despite these similarities, PN and AT3 are distinct; they differ in size and are not immunologically cross-reactive. Whereas AT3 regulates the proteolytic activity of thrombin in serum, PN may regulates the activity of serine proteases at and near the cell surface.
mesh_terms: D016564:Amyloid beta-Protein Precursor; D000990:Antithrombin III / Q000276:immunology; D002352:Carrier Proteins / Q000276:immunology / Q000502:physiology*; D002460:Cell Line; D055598:Chemical Phenomena; D002621:Chemistry; D010450:Endopeptidases / Q000378:metabolism*; D000939:Epitopes; D005347:Fibroblasts; D006493:Heparin / Q000378:metabolism; D006801:Humans; D008297:Male; D010960:Plasminogen Activators / Q000378:metabolism*; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D013917:Thrombin / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
chemical_list: D016564:Amyloid beta-Protein Precursor; D002352:Carrier Proteins; D000939:Epitopes; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D000990:Antithrombin III; D006493:Heparin; D010450:Endopeptidases; D010960:Plasminogen Activators; D013917:Thrombin; D014568:Urokinase-Type Plasminogen Activator