Introduction

Abstract

Blood coagulation and fibrinolysis are the results of the sequential activation of a group of protein-cleaving enzymes (proteinases). Many components of the coagulation and fibrinolysis pathways exsist in the circulation as enzyme precursors, which become activated when specific peptide bonds are cleaved by proteinases. These proteolytic mechanisms are controled by natural inhibitors. Five major proteinase inhibitors are known. These are α₂-macroglobulin, α₂-plasmin inhibitor, antithrombin III, α₁-antitrypsin and Cl-inactivator. General properties of the interactions of these inhibitors with enzymes and the methods to study their in vivo interactions are discussed.