THE RECOMBINANT ESCHERICHIA COLI-DERIVED PROTEASE DOMAIN OF TISSUE-TYPE PLASMINOGEN-ACTIVATOR IS A POTENT AND FIBRIN SPECIFIC FIBRINOLYTIC AGENT

The protease domain of human tissue-type plasminogen activator is expr essed in Escherichia coli as inclusion bodies. Subsequently it is conv erted into its active form by an in vitro folding process. In this stu dy we compare the in vitro activity and the specificity in a plasma mi lieu of the protease domain with that of the recombinant tissue-type p lasminogen activator isolated from Chinese hamster ovary cells. The am idolytic activity of the single chain and the two chain form of the pr otease is comparable with recombinant tissue-type plasminogen activato r thus indicating that the active site of both enzymes is similar. The plasmin forming activity and the activity in a static fibrin clot lys is assay of the protease domain is reduced by a factor of 240 and 10, respectively, as compared to recombinant tissue-type plasminogen activ ator. This may be a consequence of the missing affinity to fibrin. In contrast, the protease is equipotent and at high concentrations even m ore potent than the recombinant tissue-type plasminogen activator in a dynamic plasma model. Furthermore, the in vitro analysis of several c oagulation parameters revealed no significant differences between the protease domain and the recombinant tissue-type plasminogen activator from Chinese hamster ovary cells. In conclusion, our data demonstrate that in plasma the protease domain is a potent plasminogen activator w ith a similar fibrin specificity as CHO-t-PA.