Sigma-Aldrich, Thrombin from human plasma, ≥1,000 NIH units/mg protein (E1%/280, 18.3)

The F2 gene encodes thrombin protein and is mapped to human chromosome 11p11.2

Application

Thrombin from human plasma has been:

• dissolved in CaCl2 and added to poly ethylene glycolated fibrinogen/cell solution for fibrin production
• to polymerize fibrin on well plates
• used as an endogenous agonist proteinase for proteinase-activated receptors : PAR1, PAR3 and PAR4 for stimulation of cells

Biochem/physiol Actions

Thrombin is an endolytic serine proteasewhich stimulates vascular damage induced-leukocytes, platelets, endothelial and mesenchymal cell production. This action is mediated via G-protein-coupled receptor. It catalysis the cleavage of fibrinogen at Arg−Gly bonds to form fibrin and release fibrinopeptides A and B.The predominant form of thrombin in vivo is the zymogen prothrombin (factor II), which is produced in the liver. Prothrombin is a coagulation activation factor, high levels of which indicates cancer.Thrombin can be used to cleave fusion proteins. Cleavage of fusion proteins can be carried out at a thrombin:fusion protein ratio of 1:500.Serine protease that selectively cleaves Arg-Gly bonds in fibrinogen to form fibrin and fibrinopeptides A and B.

Unit Definition

Activity is expressed in NIH units obtained by direct comparison to a NIH Thrombin Reference Standard

Physical form

Lyophilized from saline sodium citrate buffer, pH 6.5

Analysis Note

The NIH assay procedure uses 0.2 ml diluted plasma (1:1 with saline) as a substrate and 0.1ml of thrombin sample (stabilized in a 1% buffered albumin solution) based on a modification of the method of Biggs. Only clotting times in the range of 15-25 seconds are used for determining thrombin concentrations.