Thrombin is the final coagulation protease in regard to hemostasis, promoting both procoagulant and anticoagulant effects. It is a lyophilized powder containing sucrose, sodium chloride and Tris. The predominant form of thrombin in vivo is the zymogen, prothrombin (factor II), which is produced in the liver. The concentration of prothrombin in normal human plasma is 5–10 mg/dL. Prothrombin is a glycoprotein with a glycan content of ~12%.

Thrombin is used throughout the diagnostics industry in a variety of coagulation assays, clotting factor tests and defibrination of blood or plasma for serum controls. Thrombin is also used for site specific cleavage of recombinant fusion proteins, and in biochemical and medical research applications. Bovine Thrombin, low specific activity, is manufactured from New Zealand-sourced bovine plasma using prothrombin activated with thromboplastin extracted from bovine lung tissue. Thrombin is lyophilized in glass vials under vacuum to optimize product performance. Low specific activity thrombin has 90 - 500 NIH units/mg and greater than 50% total protein. Thrombin has been used in a study to assess persistent hypocoagulability in patients with septic shock.

Prothrombin is cleaved in vivo by activated factor X, releasing the activation peptide and cleaving thrombin into light and heavy chains yielding catalytically active a-thrombin. a-Thrombin is composed of a light chain (A chain, MW ~6 kDA) and a heavy chain (B chain, MW ~31 kDa). These two chains are joined by one disulfide bond. The B chain of human thrombin consists of a peptide portion (MW 29,485 Da) and a carbohydrate portion (MW 2,334 Da) with N-linked glycosylation at three Asn residues.5,6 Bovine thrombin contains 1.7% glucosamine, 1.8% sialic acid, 0.61% galactose, and 0.95% mannose. Thrombin also contains g-carboxyglutamyl residues. These modified glutamyl residues are the result of carboxylation by a microsomal enzyme, vitamin Kdependent carboxylase. g-Carboxyglutamyl residues are necessary for the Ca²⁺ -dependent interaction with a negatively charged phospholipid surface, which is essential for the conversion of prothrombin to thrombin. Prothrombin is activated in vivo on the surface of a phospholipid membrane that binds the amino terminus of prothrombin along with factors Va and Xa. The activation process starts slowly because factor V is activated to factor Va by the initial, small amount of thrombin.

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

Activity is expressed in NIH units obtained by direct comparison to a NIH Thrombin Reference Standard, Lot K. The NIH assay procedure uses 0.2 mL of diluted plasma (1:1 with saline) as a substrate and 0.1 mL of 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 activity. Optimal clotting temperature is 37 °C.