Thrombin is an enzyme that cleaves bonds after Arg and Lys, converts fibrinogen to fibrin and activates factors V, VII, VIII. Prothrombin is activated on the surface of a phospholipid membrane where factor Xa removes the activation peptide and cleaves the remaining part into light and heavy chains. This domain corresponds to the light chain of thrombin.
Jiyao W et al.(2023). "The conserved domain database in 2023.",