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A B S T R A C T We investigated the effect of elastaselike neutral protease isolated from human granulocytes on human fibrinogen. Dependent on enzyme concentration and time of incubation, the elastase-like protease induced a progressive degradation of fibrinogen. Analysis of the remaining polypeptide chains showed a high susceptibility of the Aa-and low susceptibility of the y-chain of fibrinogen towards the proteolytic action of the enzyme. The split products were characterized by polyacrylamide gel electrophoresis and two-dimensional immunoelectrophoresis. They showed antigenic determinants of fibrinogen and of plasmin-induced proteolysis products D and E. The cleavage fragments isolated by gel chromatography had distinct molecular weights. Coagulability of fibrinogen by thrombin was inhibited according to the concentration of the protease and the time of incubation. Split products of fibrinogen with higher molecular weight prolonged the coagulation time of native fibrinogen, whereas low molecular weight fragments were ineffective.

To show whether direct proteolysis of coagulation factors may play a role in patients with so-called consumption coagulopathy, granulocytic neutral proteases in the plasma of patients with acute myelocytic leukemia and septicemia were assayed by one- and two-dimensional Laurell electrophoresis. Complexes between serum alpha1-antitrypsin and elastase-like granulocytic protease could be demonstrated in those patients with acute myelocytic leukemia and septicemia who also had moderate or severe coagulation defects. Despite the presence of a high antiprotease potential, addition of the elastase-like enzyme to normal plasma resulted in coagulation defects in vitro comparable to those seen in the patients. These results and the ability of the elastase- like protease to destroy isolated clotting factors suggested that in certain types of coagulation factor deficiencies direct proteolysis rather than consumption of clotting factors due to disseminated intravascular coagulation may be operational.

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