How is the molecular structure of thrombin have importance to its function
Thrombin catalyzes the penultimate step of blood clotting. Thrombin is synthesized in the liver and secreted into the general circulation in an inactive zymogen form (prothrombin), a complex multidomain glycoprotein that is activated to yield thrombin at sites of vascular injury by limited proteolysis following upstream activation of the coagulation cascade. Its structure is very similar to the trypsin which is a typical serine protease. It shows the presence of surface loops that partially occlude the active site and make specific contacts with residues adjacent to the scissile bond of substrates. Specificity toward macromolecular substrates and cofactors is additionally enhanced by anion-binding exosites that are spatially distinct from the active site.