C5 convertase is an enzyme complex that plays a crucial role in the immune system, specifically in the complement system. It is responsible for cleaving the complement protein C5 into two fragments, C5a and C5b. C5a acts as a potent inflammatory mediator, while C5b initiates the formation of the membrane attack complex, which helps to destroy pathogens. There are two main forms of C5 convertase: the classical/lectin pathway C5 convertase (C4b2a3b) and the alternative pathway C5 convertase (C3bBb3b). Both forms are essential for amplifying the immune response and enhancing the body's ability to fight infections.