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Related Concept Videos

Catalytically Perfect Enzymes01:07

Catalytically Perfect Enzymes

The theory of catalytically perfect enzymes was first proposed by W.J. Albery and J. R. Knowles in 1976. These enzymes catalyze biochemical reactions at high-speed. Their catalytic efficiency values range from 108-109 M-1s-1. These enzymes are also called 'diffusion-controlled' as the only rate-limiting step in the catalysis is that of the substrate diffusion into the active site. Examples include triose phosphate isomerase, fumarase, and superoxide dismutase.
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Hemostasis is a crucial process that prevents excessive blood loss from damaged blood vessels. It involves various mechanisms such as vasoconstriction, platelet adhesion and activation, and fibrin formation. The importance of each mechanism depends on the type of vessel injury. In contrast, thrombosis is the abnormal formation of a blood clot within the blood vessels, leading to potential complications if the clot obstructs blood flow. Thrombosis can be caused by increased coagulability of the...
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Factor IX mutants with enhanced catalytic activity.

R Hartmann1, M Dockal, W Kammlander

  • 1Department of Discovery Research and Technical Assessment, Baxter Innovations GmbH, Vienna, Austria.

Journal of Thrombosis and Haemostasis : JTH
|August 7, 2009
PubMed
Summary
This summary is machine-generated.

Mutations in coagulation factor IX (FIX) loop 99 enhance FIXa activity without FVIIIa, improving clotting and thrombin generation. Some FIX mutants show significantly increased FX activation efficiency, suggesting potential therapeutic applications.

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Area of Science:

  • Biochemistry
  • Hematology
  • Molecular Biology

Background:

  • Activated coagulation factor IX (FIXa) exhibits limited catalytic activity on its substrate FX without activated factor VIII (FVIIIa).
  • Loop 99 in FIXa stabilizes a conformation that restricts FX access to the active site, contributing to low activity.

Purpose of the Study:

  • To explore the impact of mutations in FIX loop 99 and the active site on FIXa activity.
  • To assess the influence of these mutations with and without FVIIIa.

Main Methods:

  • Construction and characterization of five full-length FIX mutants with amino acid substitutions in the catalytic domain.
  • Assays measuring FX activation in model systems and plasma.

Main Results:

  • Mutations Y94F and K98T in FIX enhanced clotting activity (2.5-fold) and thrombin generation (3.5-fold) in FIX-depleted plasma.
  • Two FIXa mutants (FIXa-L and FIXa-M) displayed significantly increased catalytic efficiency (17-fold and 6-fold, respectively) towards FX in the absence of FVIIIa.
  • Despite enhanced FIXa activity, zymogen forms of these mutants performed similarly to plasma-derived FIX in plasma.

Conclusions:

  • Mutations can enhance FIXa catalytic activity, particularly in the absence of FVIIIa.
  • Specific mutations improve FIX function in plasma assays, suggesting potential for modified FIX therapeutics.
  • The study indicates that mutations affect not only FIXa activity but also its stability and regulation in plasma.