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Protein C inhibitor. Purification from human plasma and characterization
The Journal of Biological Chemistry
|January 10, 1983
Summary
Researchers isolated a novel protein C inhibitor from human plasma. This inhibitor is the sole plasma component that effectively neutralizes activated protein C, crucial for blood coagulation regulation.
Area of Science:
- Biochemistry
- Hematology
- Protease Inhibitor Research
Background:
- Protein C inhibitor plays a vital role in regulating blood coagulation.
- Understanding its properties is crucial for hemostasis research.
Purpose of the Study:
- To isolate and characterize the primary inhibitor of activated protein C in human plasma.
- To determine if this inhibitor is distinct from previously identified protease inhibitors.
Main Methods:
- Multi-step chromatographic isolation from human plasma.
- Biochemical characterization including SDS-PAGE, isoelectric focusing, and agarose gel electrophoresis.
- Enzyme inhibition assays using fluorogenic substrates and activated partial thromboplastin time.
Main Results:
- A single polypeptide chain inhibitor with Mr = 57,000 was purified.
- The inhibitor exhibited heterogeneity in isoelectric points (pI) ranging from 7.4 to 8.6.
- It formed a 1:1 molar complex with activated protein C, exhibiting non-competitive inhibition (Ki = 5.8 x 10(-8) M) and blocking its procoagulant activity.
Conclusions:
- The isolated protein C inhibitor is biochemically and immunologically distinct from known plasma protease inhibitors.
- This purified inhibitor is identified as the sole inhibitor of activated protein C in human plasma.