Effect of human granulocytic elastase on isolated human antithrombin III

The interaction of elastase isolated from human granulocytes with purified human antithrombin III was investigated. Antithrombin III did not display any inhibitory effect on granulocytic elastase. Dependent on enzyme concentration, however, granulocytic elastase induced progressive inactivation of antithrombin III leading to an almost complete loss of the thrombin inhibitory activity at a molar ratio of elastase: antithrombin III = 0.4:1 within 5 min at 25 degrees C. Antithrombin III is not drastically degraded by elastase as revealed by polyacrylamide gel electrophoretic and rocket immunoelectrophoretic investigations. However, characterization by two-dimensional immunoelectrophoresis with heparin in the first dimensional gel layer revealed a distinct change in the electrophoretic mobility of the inhibitor preincubated with elastase compared to native antithrombin III. This indicates that heparin binding sites of antithrombin III are occupied or affected by the elastase-induced peptide bond cleavage(s). Granulocytic proteinase inhibitors (eglin, Bowman-Birk inhibitor) proved to be highly effective in preventing the antithrombin III inactivation by degradation due to elastase. It is assumed that at least part of the antithrombin III consumption in diseases such as septicemia or endotoxemia is due to proteolysis by granulocytic proteinases. Application of specific inhibitors in the early phase of these ailments should be able to prevent this unspecific degradation of the endogenous antithrombin III.