Determination of a new rapid plasmin inhibitor in human blood by means of a plasmin specific tripeptide substrate

Abstract

A method for determination of antiplasmin activity is presented. Plasmin and plasma are incubated, and the remaining plasmin activity is measured spectrophotometrically by means of the plasmin specific tripeptide substrate H-D-Val-L-Leu-L-Lys-p-nitroanilide. The method is simple, rapid and easily automatized. By the immunoadsorption technique, and with the aid of purified substances it is shown that the measured activity is mainly due to a new antiplasmin [2, 4] and possibly to some extent to α₂-macroglobulin. Antithrombin III in the absence of heparin, α₁-antitrypsin and C₁-esterase inhibitor have no antiplasmin activity in the method. Heparin and epsilonaminocaproic acid interfered with the assay.

Key Words:

• antithrombin
• antiplasmin
• epsilonaminocaproic acid
• fibrinolysis
• heparin
• immunochemistry
• α₂-macroglobulin
• plasmin