Description_x000D_ Application_x000D_ Fusion proteins are commonly expressed with a factor Xa cleavable Ile-Glu (or Asp)-Gly-Arg-↓-X sequence. Typically 1 mg of fusion protein can be incubated with 10 μg of factor Xa for 2.5 hours at 37 °C._x000D_ Biochem/physiol Actions_x000D_ Factor Xa catalyzes the hydrolysis of the Arg-Thr and then Arg-Ile bonds in prothrombin to yield active thrombin._x000D_ The fairly strict recognition sequence is Ile-Glu (or Asp)-Gly-Arg-↓-X._x000D_ It may sometimes cleave at other basic residues, depending on the conformation of the target protein. Factor Xa will not cleave if a proline residue follows the arginine of the recognition sequence._x000D_ pH Optimum: 7.6-8.0_x000D_ Temperature Optimum: 37 °C_x000D_ Physical properties_x000D_ Factor Xa is a serine endoproteinase and a member of the S1 peptidase family. Factor Xa plays a critical role in the coagulation cascade by catalyzing the proteolytic conversion of prothrombin to active thrombin. Factor Xa′s prothrombin conversion activity is greatly enhanced in vivo when complexed with factor V, calcium ions and phospholipids on the activated platelet surface._x000D_ The zymogen form, Factor X, is activated in vivo by two different pathways. The intrinsic pathway utilizes a catalytic complex composed of factor IXa, factor VIII, phospholipids and calcium ions. The extrinsic pathway utilizes a complex of factor VII and tissue factor. The factor X zymogen is a 55 KDa glycoprotein with a light and heavy chain joined by a single disulfide._x000D_ Unit Definition_x000D_ One unit of activated Factor X will liberate 1.0 μmole of p-nitroanilide from N-benzoyl-L-isoleucyl-L-glutamyl-L-glycyl-L-arginine-p-nitroaniline per minute at pH 8.3 at 37 °C.