Tenase
Encyclopedia
In coagulation
, the procoagulant protein factor X
can be activated into factor Xa two ways. Extrinsic and intrinsic ways.
The activating complexes are called tenase. Tenase is a contraction of "ten" and the suffix "-ase", which means, that the complex activate its substrate (inactive factor X) 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
(IXa), its cofactor factor VIII
(VIIIa), the substrate (factor X), and they are activated by negatively charged surfaces (such as glass, active platelet
membrane, sometimes cell membrane
of monocytes). 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.
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
, the procoagulant protein factor X
Factor X
Factor X, also known by the eponym Stuart-Prower factor or as prothrombinase, is an enzyme of the coagulation cascade. It is a serine endopeptidase .-Physiology:...
can be activated into factor Xa two ways. Extrinsic and intrinsic ways.
The activating complexes are called tenase. Tenase is a contraction of "ten" and the suffix "-ase", which means, that the complex activate its substrate (inactive factor X) by cleaving it.
Extrinsic tenase complex is made up of tissue factor
Tissue factor
Tissue factor, also called platelet tissue factor, factor III, thrombokinase, or CD142 is a protein present in subendothelial tissue, platelets, and leukocytes necessary for the initiation of thrombin formation from the zymogen prothrombin. An incorrect synonym is thromboplastin...
, factor VII
Factor VII
Factor VII is one of the proteins that causes blood to clot in the coagulation cascade. It is an enzyme of the serine protease class. A recombinant form of human factor VIIa has U.S. Food and Drug Administration approval for uncontrolled bleeding in hemophilia patients...
, and Ca2+ as an activating ion.
Intrinsic tenase complex contains the active factor IX
Factor IX
Factor IX is one of the serine proteases of the coagulation system; it belongs to peptidase family S1. Deficiency of this protein causes hemophilia B. It was discovered in 1952 after a young boy named Stephen Christmas was found to be lacking this exact factor, leading to...
(IXa), its cofactor factor VIII
Factor VIII
Factor VIII is an essential blood clotting factor also known as anti-hemophilic factor . In humans, Factor VIII is encoded by the F8 gene...
(VIIIa), the substrate (factor X), and they are activated by negatively charged surfaces (such as glass, active platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
membrane, sometimes cell membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
of monocytes). These vitamin K
Vitamin K
Vitamin K is a group of structurally similar, fat soluble vitamins that are needed for the posttranslational modification of certain proteins required for blood coagulation and in metabolic pathways in bone and other tissue. They are 2-methyl-1,4-naphthoquinone derivatives...
-dependent procoagulant factors dock to this surface through their Gla domain
Gla domain
Vitamin K-dependent carboxylation/gamma-carboxyglutamic domain is a protein domain that contains post-translational modifications ofmany glutamate residues by vitamin K-dependent carboxylation to form gamma-carboxyglutamate . The Gla residues are responsible for the high-affinity binding of...
with Ca2+ bridges. This makes the activating process much faster and blocks the binding of inhibitors.