Incoagulation, thecoagulation factor X can be activated intofactor Xa in two ways: either extrinsically or intrinsically.
The activating complexes are together calledtenase. Tenase is ablend word of "ten" and the suffix "-ase", which means, that the complex activates its substrate (inactive factor X) by cleaving it.[1]
Extrinsic tenase complex is made up oftissue factor,factor VII, andCa2+ as an activating ion.
Intrinsic tenase complex contains the activefactor IX (IXa), its cofactorfactor VIII (VIIIa), the substrate (factor X), and they are activated by negatively charged surfaces (such as glass, activeplatelet membrane, sometimescell membrane ofmonocytes). Thesevitamin K-dependent procoagulant factors dock to this surface through theirGla domain with Ca2+ bridges.