Analysis Note

The NIH assay procedure uses 0.2 mL of diluted plasma (1:1 with saline) as a substrate and 0.1 mL 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.

Activity is expressed in NIH units obtained by direct comparison to a NIH Thrombin Reference Standard, Lot K.

Application

Thrombin from bovine plasma has been used to study its effect on the perinatal rat subventricular zone cells and oligodendrocyte precursor cell proliferation, differentiation, and migration in culture. It has also been used in fibrin degradation assay to measure nattokinase activity.

Thrombin is used for site specific cleavage of recombinant fusion proteins containing an accessible thrombin recognition site for removal of affinity tags. Thrombin has been used in a study to assess global haemostasis and point of care testing.

Biochem/physiol Actions

Thrombin is a proteolytic enzyme critical in the blood clotting process and activates clotting factors V, VIII, XI, and XII. Thrombin promotes platelet aggregation. Therefore, thrombin is the final coagulation protease in hemostasis, promoting both procoagulant and anticoagulant effects. It is used to treat bleeding from capillaries and small venules.

Serine protease that selectively cleaves Arg-Gly bonds in fibrinogen to form fibrin and fibrinopeptides A and B.

General description

Thrombin is a sodium-activated type II enzyme. It contains two anion binding exosites, ABE-I and ABE-II. The predominant form of thrombin in vivo is the zymogen prothrombin (factor II), which is produced in the liver. Bovine a-thrombin consists of a light chain (A chain) and a heavy chain (B chain). These two chains are joined by one disulfide bond. The B chain of a-thrombin includes a carbohydrate portion.

Other Notes

View more information on thrombin at www.sigma-aldrich.com/enzymeexplorer.

Physical form

Lyophilized from saline sodium citrate buffer, pH 6.5

Unit Definition

Activity is expressed in NIH units obtained by direct comparison to a NIH thrombin reference standard.