Action of Brinase on human fibrinogen and plasminogen

Brinase added to human plasma in vitro caused a decrease in fibrinogen concentration, positive paracoagulation tests and formation of a friable clot in sequence. Agarose gel filtration of these samples revealed the presence of fibrinogen derivatives both larger and smaller than the parent molecule. Infusion of the enzyme in vivo resulted in a decreased fibrinogen level, a prolonged thrombin time and an increase in fibrinogen related antigen (FRA) in serum. The elution pattern of FRA in the plasma samples obtained after infusion of Brinase was similar to that of the in vitro samples. The plasma pool of fibrinogen was partially consumed by infusion of Brinase, but the turnover of plasminogen remained unaffected. Purified plasminogen was partially degraded by addition of the enzyme but this was not accompanied by a generation of proteolytic activity. These findings confirm that Brinase induces a proteolytic degradation of fibrinogen in plasma without activation of the plasminogen-plasmin system. Exposure of polymerization site(s) in the fibrinogen molecule is probably responsible for the reported clot promoting effect of the enzyme.