The inhibition of human plasma Kallikrein by antithrombin III

Abstract

Prekallikrein, prekallikrein activator, high molecular weight kininogen and antithrombin III were isolated from human plasma. The prekallikrein was converted to kallikrein by prekallikrein activator. The kallikrein had arginine esterase activity and generated kinin from kininogen. Both activities were inhibited by antithrombin III in concentrations of approximately 1 2 of that of plasma. Physiological concentrations of heparin were required for the rapid and complete inhibition of kallikrein. In the absence of heparin only partial and much slower inhibition was achieved. The proteolytic, i.e. kinincleaving activity of kallikrein was more readily inhibited than the esterolytic activity.