Measurement of Procarboxypeptidase U (TAFI) in Human Plasma: A Laboratory Challenge

(CPU) as a novel regulator of the fibrinolytic rate has attracted much interest during recent years. CPU circu-lates in plasma as a zymogen, proCPU, that can be activated by thrombin, thrombin-thrombomodulin (T-Tm), or plasmin. Given that the proCPU concentration in plasma is far below its Km for activation by the T-Tm complex, the formation of CPU will be directly propor-tional to the proCPU concentration. A low or high proCPU plasma concentration might therefore tip the balance between profibrinolytic and antifibrinolytic pathways and thereby cause a predisposition to bleed-ing or thrombosis. Content: To measure plasma proCPU concentrations, different methods have been developed based on 2 different principles: antigen determination and mea