thrombin blood-clotting enzyme: human alpha-thrombin molecule is a key protein in the blood coagulation cascade. converts soluble

pdb1ppb thrombin alpha coagulation factor blood activated prothrombin plasma cascade thrombus clot fibrin clotting vitamin antithrombin inhibitor direct anticoagulant thinner hirudin argatroban melagatran ximelagatran dabigatran structure peptide protein amino acid molecule polypeptide polymer atoms