Comparison of recombinant tissue-type plasminogen activator (rt-PA) expressed in mouse C127 cells and human vascular plasminogen activator (HV-PA)

Tissue-type plasminogen activator produced by recombinant DNA technology (rt-PA) has now been recognized as a promising clot-selective thrombolytic agent. We have compared the properties of rt-PA expressed in mouse C127 cells with those of naturally occurring human vascular plasminogen activator (HV-PA). The molecular weight of HV-PA and rt-PA was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to be approx. 66,000. HV-PA and rt-PA were labile and rapidly lost their activities at pH values below 5.5. The optimum pH of HV-PA and rt-PA for plasminogen activation was around 8.5. HV-PA and rt-PA appeared to be very similar in amidolytic properties, amino-acid composition and carbohydrate composition. Moreover, the N-terminal amino-acid sequence of HV-PA was in good agreement with that of rt-PA. The purified preparations of HV-PA and rt-PA had specific activities of about 250,000 and 600,000 IU/mg, respectively. Both activators bound to fibrin clots to similar degree. In immunodiffusion as well as in the quenching experiments of the fibrinolytic activities, rt-PA appeared to be immunodiffusion as well as in the quenching experiments of the fibrinolytic activities, rt-PA appeared to be immunologically indistinguishable from HV-PA. All these findings indicate that rt-PA expressed in mouse C127 cells is identical with naturally occurring HV-PA in physical and chemical properties.