Abstract
Biochemically, DIC is an abnormality consisting of elevated proteolysis in the systemic circulation. The enzymes participating in DIC are serine proteases which involve the systems of coagulation, fibrinolysis and kinin formation. This paper describes a brief review of proteolytic events observed in coagulation·fibrinolysis and kinin-formation. In DIC, there occur stpewise chain reactions of limited proteolysis of each factor of the systems. For activation of the zymogens shown in parentheses, the following clevages of peptide bonds are necessary: Arg-Val (XII), Arg-Ile (XI), Arg-Ala and Arg-Val (IX), Arg-Ile (VII and X), Arg-Ile, A rg-Thr and Arg-Ser (Prothrombin), Arg-Gly (XIII) and Arg-Val, Lys-Lys (Plasminogen). The terminal substrates, fibrinogen in coagulation, fibrino (gen) in fibrin (ogen) olysis and high molecular weight kininogen in kinin formation, recieve their limited proteolysis in such peptide bonds as Arg-Gly of Aα and Bβ chains of fibrinogen by thrombin, Arg- or Lys- of fibrin (ogen) by plasmin, Lys-Arg and Arg-Ser of HMW kininogen by kallikrein, generating fibrin, fibrin (ogen) degradation products and bradykinin, respectively. Some of activated enzymes, especially thrombin exert positive or negative control activities, and some of peptide fragments released by limited proteolysis show usually negative ones.
