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Plasminogen mutants activated by thrombin. Potential thrombus-selective thrombolytic agents
K M Dawson1, A Cook, J M Devine
1British Bio-technology Ltd, Oxford, United Kingdom.
The Journal of Biological Chemistry
|June 10, 1994
Summary
Researchers engineered plasminogen to be activated by thrombin, a blood clotting enzyme. This novel thrombolytic agent targets clots by generating plasmin directly at the thrombus site.
Area of Science:
- Biochemistry
- Molecular Biology
- Hematology
Background:
- Plasminogen activation is crucial for fibrinolysis (clot breakdown).
- Current plasminogen activators have limitations in targeting thrombi.
- Thrombin is a key enzyme in the blood coagulation cascade.
Purpose of the Study:
- To develop a novel thrombolytic agent by modifying plasminogen activation.
- To create a plasminogen variant activated by thrombin, not conventional activators.
- To achieve thrombus-specific plasmin generation for enhanced clot lysis.
Main Methods:
- Engineered plasminogen variants with thrombin-cleavable sequences.
- Substituted plasminogen cleavage site residues with sequences from thrombin-cleavable proteins (e.g., fibrinogen, factor XI).
- Assessed thrombin cleavage kinetics and in vitro clot lysis efficacy of variants.
Main Results:
- Plasminogen variants showed varying cleavage rates by thrombin.
- A variant with factor XI sequence (T51) was rapidly cleaved by thrombin.
- This T51 variant demonstrated effective clot lysis, indicating thrombin-induced activation.
- The engineered plasminogen generates fibrinolytic activity localized to thrombi.
Conclusions:
- Thrombin-activatable plasminogen offers a novel mechanism for targeted thrombolysis.
- This approach bypasses physiological hemostatic mechanisms for localized fibrinolysis.
- The engineered agent has potential for selective plasmin generation and prolonged action at the clot site.