Tenase
In coagulation, the procoagulant protein factor X can be activated into factor Xa two ways; extrinsically or intrinsically.
The activating complexes are called tenase. Tenase is a contraction of "ten" and the suffix "-ase", which means, that the complex activates its substrate by cleaving it.
Extrinsic tenase complex is made up of tissue factor, factor VII, and Ca2+ as an activating ion.
Intrinsic tenase complex contains the active factor IX, its cofactor factor VIII, the substrate, and they are activated by negatively charged surfaces. These vitamin K-dependent procoagulant factors dock to this surface through their Gla domain with Ca2+ bridges. This makes the activating process much faster and blocks the binding of inhibitors.
