Coagulase

Coagulase is an adhesin (EC 3.4.23.48) produced by Staphylococcus aureus to localize an area of residence that converts fibrinogen to fibrin. In laboratory, it is used to distinguish between different types of Staphylococcus isolates. Coagulase negativity excludes S. aureus.

Coagulase is not an enzyme, despite its ending (ase). It reacts with prothrombin in the blood. The resulting complex is called staphylothrombin, which causes blood to clot by converting fibrinogen to fibrin. Some coagulase is tightly bound to the surface of the bacteria, S. aureus, and coats its surface with fibrin upon contact with blood. Fibrin-coated staphylococci resist phagocytosis making the bacteria more virulent.