C5 plays a central role in both the classical and the alternative pathway of complement activation. C5 is cleaved by C5 CONVERTASE into complement c5a and complement c5b. The smaller fragment C5a is an ANAPHYLATOXIN and mediator of inflammatory process. The major fragment C5b binds to the membrane initiating the spontaneous assembly of the late complement components, C5-C9, into the MEMBRANE ATTACK COMPLEX.