The plasminogen activator/plasmin system plays a crucial role in extracellular matrix (ECM) degradation and regulation of proteolytic and antiproteolytic activities. Two main enzymes, urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA), are key participants in this system. Both are serine proteases with distinct targeting determinants and functions. uPA binds to a plasma membrane receptor, while tPA binds to ECM components like fibrin. These enzymes, along with their inhibitors (PAIs), regulate ECM turnover and cell migration. Plasminogen, the primary substrate for PAs, is activated by uPA and tPA to form plasmin, a broad-spectrum serine protease that contributes to ECM degradation and other cellular processes. PAIs, particularly PAI-1 and PAI-2, inhibit PAs and regulate their activity. The system is also involved in cell surface binding, where uPA and plasminogen can bind to cell surfaces, enhancing proteolysis and focusing enzyme activity in specific regions. The expression and regulation of PAs and PAIs are influenced by hormones, growth factors, and other signaling pathways. The PA/plasmin system is involved in various physiological and pathological processes, including embryonic development, ovulation, inflammation, wound healing, angiogenesis, and cancer progression. It also plays a role in the maintenance of fluidity in tubular structures and in the processing of growth factors and hormones. The system's dynamic regulation and multifunctional roles highlight its importance in cellular and tissue homeostasis.The plasminogen activator/plasmin system plays a crucial role in extracellular matrix (ECM) degradation and regulation of proteolytic and antiproteolytic activities. Two main enzymes, urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA), are key participants in this system. Both are serine proteases with distinct targeting determinants and functions. uPA binds to a plasma membrane receptor, while tPA binds to ECM components like fibrin. These enzymes, along with their inhibitors (PAIs), regulate ECM turnover and cell migration. Plasminogen, the primary substrate for PAs, is activated by uPA and tPA to form plasmin, a broad-spectrum serine protease that contributes to ECM degradation and other cellular processes. PAIs, particularly PAI-1 and PAI-2, inhibit PAs and regulate their activity. The system is also involved in cell surface binding, where uPA and plasminogen can bind to cell surfaces, enhancing proteolysis and focusing enzyme activity in specific regions. The expression and regulation of PAs and PAIs are influenced by hormones, growth factors, and other signaling pathways. The PA/plasmin system is involved in various physiological and pathological processes, including embryonic development, ovulation, inflammation, wound healing, angiogenesis, and cancer progression. It also plays a role in the maintenance of fluidity in tubular structures and in the processing of growth factors and hormones. The system's dynamic regulation and multifunctional roles highlight its importance in cellular and tissue homeostasis.