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Thrombin-catalyzed activation of human coagulation factor V
The Journal of Biological Chemistry
|June 10, 1982
Summary
Human coagulation factor V activation by thrombin yields factor Va, a significantly more active cofactor. The process involves specific peptide bond cleavages, producing distinct fragments essential for biological activity.
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Human coagulation factor V is a crucial protein in the blood clotting cascade.
- Understanding factor V activation is vital for hemostasis research.
Purpose of the Study:
- To elucidate the activation pathway of human coagulation factor V by thrombin.
- To characterize the resulting fragments and their role in factor Va activity.
Main Methods:
- Purification of single-chain human factor V from plasma.
- Limited proteolysis of purified factor V using thrombin.
- Analysis of activation intermediates and end products via molecular weight and N-terminal sequencing.
- Reconstitution experiments with isolated fragments.
Main Results:
- Purified factor V (Mr = 330,000) consists of a single polypeptide chain.
- Thrombin activation generates factor Va with 25-30 fold higher cofactor activity.
- Activation produces specific intermediates and end products, including fragments D, E, C1, and F1F2.
- Fragments D and F1F2, held noncovalently, reconstitute the active factor Va molecule.
Conclusions:
- The thrombin-catalyzed activation of human factor V follows a distinct cleavage order compared to bovine factor V.
- The biologically active factor Va molecule is composed of noncovalently associated fragments D and F1F2.
- Activation peptides E and C1 are derived from the interior of the factor V molecule.