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Making tissue-type plasminogen activator more fibrin specific
N F Paoni1, A M Chow, L C Peña
1Department of Cardiovascular Research, Genetech, Inc., South San Francisco, CA 94080.
Protein Engineering
|July 1, 1993
Summary
Mutagenesis of tissue-type plasminogen activator (t-PA) at specific protease domain sites enhances fibrin specificity. These modifications reduce fibrinogen activity while maintaining normal fibrin activity, improving t-PA
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Engineering
Background:
- Tissue-type plasminogen activator (t-PA) is a crucial enzyme in fibrinolysis.
- Enhancing t-PA's fibrin specificity is key to improving its therapeutic applications.
- Previous studies identified potential sites for t-PA mutagenesis.
Purpose of the Study:
- To investigate the impact of mutagenesis at specific protease domain sites on t-PA's fibrin specificity.
- To analyze the kinetic properties of t-PA variants with mutations in key functional regions.
Main Methods:
- Site-directed mutagenesis was performed at four identified regions within the t-PA protease domain.
- Kinetic analysis (kcat, Km) was conducted for wild-type and mutant t-PA in the presence of fibrinogen and fibrin.
- Mutagenesis sites included I276, KHRR 296-299, DDD 364-366, and residues H432, R434, D460, R462, and PQANL 466-470.
Main Results:
- Mutations at all investigated sites significantly reduced fibrinogen-stimulated activity.
- Fibrin-stimulated activity remained normal or increased for most variants.
- Mutations at KHRR 296-299 uniquely increased both kcat and Km in the presence of fibrin, suggesting a direct interaction modulation.
Conclusions:
- Targeted mutagenesis of the t-PA protease domain can effectively enhance fibrin specificity.
- Mutations alter the enzyme's catalytic efficiency differently in the presence of fibrinogen versus fibrin.
- Additive effects of combined mutations suggest a combinatorial approach to optimize t-PA function.