HUMAN-LEUKOCYTE ELASTASE AND CATHEPSIN-G INACTIVATE FACTOR-VII BY LIMITED PROTEOLYSIS

The effect of supernatant from phorbol myristate acetate (PMA) stimula ted human polymorphonuclear granulocytes (PMN) on human factor VII was studied in vitro. The supernatant caused a rapid loss in factor VII c oagulant activity by the action of human leukocyte elastase (HLE) and cathepsin G in the supernatant, as demonstrated by the use of specific inhibitors of the two serine proteases, respectively. Preincubation o f the supernatant with the elastase inhibitor and the cathepsin G inhi bitor preserved 80% and 25% of the clotting activity, respectively. Ca lcium protected factor VII completely from the supernatant mediated in activation. Cathepsin G and HLE purified from PMN each destroyed the c oagulant activity of factor VII when added to a non-plasma system. The re were, however, no effect on factor VII activity when cathepsin G wa s added to plasma. Polyacrylamide gel electrophoresis in the presence of SDS indicated that HLE and cathepsin G cleaved the zymogen in the s ame manner, producing (a) peptide(s) of low molecular mass and a singl e large product of 48 kDa. Preincubation of factor VII with calcium io ns inhibited the proteolytic action of HLE and cathepsin G. It is sugg ested that HLE and cathepsin G from activated granulocytes may be part ly responsible for the loss in factor VII activity that is observed du ring sepsis.