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Structural elements that govern the substrate specificity of the clot-dissolving enzyme plasmin
Ryan B Turner1, Lin Liu, Irina Y Sazonova
1Cardiovascular Biology Laboratory, Harvard School of Public Health and the Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
The Journal of Biological Chemistry
|June 25, 2002
Summary
Modifying plasmin's loop structures with factor D sequences enhanced its clot-dissolving abilities and resistance to inhibitors. These changes improved fibrin degradation in plasma clots, suggesting potential for improved thrombolytic therapies.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Plasmin and factor D share homologous core structures but have distinct functions.
- Sequence variations in loop regions may dictate unique substrate and inhibitor interactions.
Purpose of the Study:
- To investigate the role of plasmin's loop structures in substrate and inhibitor interactions.
- To explore the potential of modifying these loops for enhanced fibrinolytic activity.
Main Methods:
- Constructed recombinant microplasminogens by incorporating factor D sequences into plasmin's loops 3, 5, and 7.
- Assessed the activity of chimeric microplasminogens using urokinase and streptokinase.
- Evaluated resistance to alpha(2)-antiplasmin and fibrin degradation in plasma clots.
Main Results:
- Chimerization abolished functional interaction with streptokinase but not complex formation.
- Microplasmin chimeras exhibited increased resistance to alpha(2)-antiplasmin.
- Chimerization minimally affected small substrate cleavage but enhanced fibrin degradation in plasma clots.
Conclusions:
- Plasmin's protease domain loop regions are critical for interactions with substrates, regulators, and inhibitors.
- Loop modification offers a promising strategy for enhancing plasmin's clot-dissolving efficacy.
- This approach could lead to improved therapeutic agents for treating thrombotic diseases.