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[Complex formation of ulinastatin with alpha-thrombin].
K Mimura1, K Shinozawa, T Kobayashi
1Medical Technology, Toyo Public Health College, Tokyo.
Rinsho Byori. the Japanese Journal of Clinical Pathology
|September 1, 1992
Summary
Ulinastatin noncompetitively inhibits alpha-thrombin, reducing its maximum velocity. A complex forms between ulinastatin, alpha-thrombin, and AT-III, suggesting distinct inhibitory mechanisms compared to thrombomodulin.
Area of Science:
- Biochemistry
- Pharmacology
Background:
- Alpha-thrombin plays a crucial role in coagulation.
- Ulinastatin is a protease inhibitor with potential anticoagulant properties.
Purpose of the Study:
- To elucidate the inhibition mechanism of ulinastatin on alpha-thrombin.
- To characterize the interaction between ulinastatin, alpha-thrombin, and AT-III.
Main Methods:
- Lineweaver-Burk double reciprocal plotting to determine enzyme kinetics.
- SDS-PAGE and Western blotting to analyze protein complex formation.
Main Results:
- Ulinastatin exhibited noncompetitive inhibition of alpha-thrombin, with a Ki of 1.05 x 10(-2) M.
- Ulinastatin reduced alpha-thrombin's Vmax from 24 U/l to 15 U/l.
- A complex comprising ulinastatin, alpha-thrombin, and AT-III was identified.
Conclusions:
- Ulinastatin acts as a noncompetitive inhibitor of alpha-thrombin.
- The formation of a ternary complex suggests a unique inhibitory pathway.
- Ulinastatin's distinct binding site on alpha-thrombin differentiates its mechanism from thrombomodulin.