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Published on: September 9, 2012
Activation of human factor IX (Christmas factor)
The Journal of Clinical Investigation
|June 1, 1978
Summary
Human Factor IX (Christmas factor), a key protein in blood coagulation, is activated by Factor XIa into Factor IXa. This process involves specific peptide bond cleavages and results in a serine protease essential for hemostasis.
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Human Factor IX (Christmas factor) is a glycoprotein crucial for blood coagulation.
- It functions as a zymogen in the intrinsic pathway, requiring activation to become enzymatically active.
Purpose of the Study:
- To elucidate the activation mechanism of human Factor IX.
- To characterize the resulting active serine protease, Factor IXa.
- To investigate the interaction of Factor IXa with antithrombin III.
Main Methods:
- Analysis of Factor IX activation by Factor XIa and Russell's viper venom.
- Peptide bond cleavage site identification.
- Molecular weight determination of precursor and active forms.
- Amino-terminal sequencing of Factor IXa chains.
- Inhibition studies with antithrombin III.
Main Results:
- Factor IX activation by Factor XIa involves cleavage of two peptide bonds, releasing an activation peptide and forming Factor IXa (composed of light and heavy chains).
- Factor IXa heavy chain contains the active site serine.
- Activation by Russell's viper venom involves a single cleavage.
- Human Factor IXa forms a complex with antithrombin III, inhibiting its activity.
Conclusions:
- The activation of human Factor IX by Factor XIa is a multi-step process involving specific proteolytic cleavages.
- The resulting Factor IXa is a serine protease inhibited by antithrombin III.
- The activation and inhibition mechanisms are similar to those observed in bovine Factor IX.
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