C5 convertase is an enzyme complex that plays a crucial role in the complement system, which is part of the immune response. It is responsible for cleaving the 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: C4b2a3b in the classical and lectin pathways, and C3bBb3b in the alternative pathway. Both forms are essential for amplifying the immune response and enhancing the body's ability to fight infections.