Thrombin is the principal enzyme of hemostasis. It catalyzes the conversion of fibrinogen to fibrin and activates procoagulant factors V, VIII, XI, and XIII. Additionally, when bound to thrombomodulin, it activates protein C, an anticoagulant zymogen.
The building blocks of proteins are amino acids, which are small organic molecules that consist of an alpha (central) carbon atom linked to an amino group, a carboxyl group, a hydrogen atom, and a variable component called a side chain (see below).
Clot retraction is the "shrinking" of a blood clot over a number of days. In doing so, the edges of the blood vessel wall at the point of injury are slowly brought together again to repair the damage that occurred.
Plasminogen is a secreted protein that upon cleavage by urokinase plasminogen activator (uPA) or tissue plasminogen activator (tPA) is converted to plasmin, a broad range protease capable of cleaving fibrin and other ECM components.
Thrombin is a serine protease: a protein-cutting enzyme that uses a serine amino acid to perform the cleavage.
The general structure of globular proteins (Thrombin) is on the right."
Prothrombin (factor II) is a soluble 72-kDa protein that is produced by the liver. It is activated to thrombin (factor IIa) via enzymatic cleavage of two sites by activated FX (FXa). Activated thrombin leads to cleavage of fibrinogen into fibrin monomers that, upon polymerization, form a fibrin clot.
The thrombin time evaluates that part of the hemostatic process where soluble fibrinogen is changed into fibrin threads. It measures the time required for a fibrin clot to form following the addition of a standard amount of thrombin to plasma.
Thrombin
| PubChem CID | 65045 |
|---|
| Molecular Formula | C12H10ClN3S |
| Synonyms | Thrombin Thionine 635-76-7 7-iminophenothiazin-3-amine;hydrochloride AI3-08874 More |
| Molecular Weight | 263.75 |
| Parent Compound | CID 65044 (3-Imino-3H-phenothiazin-7-amine) |
Currently, four parenteral direct inhibitors of thrombin activity are FDA-approved in North America: lepirudin, desirudin, bivalirudin and argatroban. Of the new oral DTIs, dabigatran etexilate is the most studied and promising of these agents.
Thrombin activates platelets through protease-activated receptors (PAR) on the platelet surface via GPCR. The most important is the activation of the GP IIb/IIIa receptor which results in the cross-linking of fibrinogen or vWF between receptors, leading to platelet aggregation.
It is a serine protease with essential functions in blood coagulation and in numerous other regulatory processes. Known natural substrates for thrombin include coagulation factors V, VIII, XI and XIII, protein C and fibrinogen [4].
Thrombin is a α/β heterodimer composed of a 36 amino acid A chain and 259 amino acid B chain connected by a disufide bridge between Cys1 and Cys122, in addition to 3 other intrachain disulfide bonds. Its overall fold is similar to trypsin and chymotrypsin and it belongs to the peptidase S1 protease family.
Thromboplastin (TPL) or thrombokinase is a mixture of both phospholipids and tissue factor found in plasma aiding blood coagulation through catalyzing the conversion of prothrombin to thrombin. However, partial thromboplastin is just phospholipids, and not tissue factor.
Thrombin converts fibrinogen, a blood clotting factor that is normally dissolved in blood, into long strands of fibrin that radiate from the clumped platelets and form a net that entraps more platelets and blood cells.
Preparation. Thrombin can be prepared from blood plasma. The preparation involves three main steps: isolation of prothrombin from plasma, activation to thrombin, and purification of the mature enzyme from the activation mixture.
Check All That Apply Osmolarity: 280-296 mOsm/L PH: 7.35 - 7.45 Platelet count: 1.000/microliter Volume in females: 4-5 L; volume in males: 5-6 L Osmolarity: 280-296 mOsm/L pH: 7.35 - 7.45 Platelet count: 1.000/microliter Volume in females: 4-5 L; volume in males: 5-6 L Total WBC count: 5,000.
is that prothrombin is (protein) a glycoprotein, produced in the liver, that is converted into thrombin during bleeding and subsequent clotting while thrombin is (enzyme) an enzyme in blood that facilitates blood clotting by converting fibrinogen to fibrin (by means of ionized calcium).
Prothrombin is a blood clotting protein that is needed to form fibrin.
Proteases, being themselves proteins, are cleaved by other protease molecules, sometimes of the same variety. This acts as a method of regulation of protease activity. Some proteases are less active after autolysis (e.g. TEV protease) whilst others are more active (e.g. trypsinogen).
Using ultrasound-guided direct visualization, thrombin is slowly injected percutaneously into the sac of the pseudoaneurysm until flow within the pseudoaneurysm has ceased; most authors recommend using 1-ml syringes of thrombin and administering this dose slowly over 10 seconds.
Thrombin exerts its hemostatic and thrombotic effects through the coagulation–inflammation axis, where it cleaves fibrinogen to generate an insoluble fibrin clot; amplifies its own production through pro-cofactor activation; and activates various cell types via proteolytic cleavage of PARs (reviewed in Coughlin32).
