Plasmin dissolves the fibrin of blood clots and acts as a proteolytic factor in a variety of other processes including embryonic development, tissue remodeling, tumor invasion, and inflammation. In ovulation, weakens the walls of the Graafian follicle. It activates the urokinase-type plasminogen activator, collagenases and several complement zymogens, such as C1 and C5. Cleavage of fibronectin and laminin leads to cell detachment and apoptosis. Also cleaves fibrin, thrombospondin and von Willebrand factor. Its role in tissue remodeling and tumor invasion may be modulated by CSPG4. Binds to cells (By similarity). Angiostatin is an angiogenesis inhibitor that blocks neovascularization and growth of experimental primary and metastatic tumors in vivo. Preferential cleavage: Lys-|-Xaa > Arg-|-Xaa, higher selectivity than trypsin. Converts fibrin into soluble products. Converted into plasmin by plasminogen activators, both plasminogen and its activator being bound to fibrin. Cannot be activated with streptokinase. Interacts (both mature PLG and the angiostatin peptide) with AMOT and CSPG4. Interacts (via the Kringle domains) with HRG; the interaction tethers PLG to the cell surface and enhances its activation. Interacts (via Kringle 4 domain) with ADA; the interaction stimulates PLG activation when in complex with DPP4. Angiostatin: Interacts with ATP5F1A; the interaction inhibits most of the angiogenic effects of angiostatin. Locates to the cell surface where it is proteolytically cleaved to produce the active plasmin. Interaction with HRG tethers it to the cell surface (By similarity). Kringle domains mediate interaction with CSPG4. In the presence of the inhibitor, the activation involves only cleavage after Arg-581, yielding two chains held together by two disulfide bonds. In the absence of the inhibitor, the activation involves additionally the removal of the activation peptide (By similarity). Plasmin is inactivated by alpha-2-antiplasmin immediately after dissociation from the clot. In the presence of the inhibitor, the activation involves only cleavage after Arg-581, resulting in 2 chains held together by 2 disulfide bonds. Without the inhibitor, the activation involves also removal of the activation peptide. Belongs to the peptidase S1 family. Plasminogen subfamily.