Complement C5, also named C3 and PZP-like alpha-2-macroglobulin domain-containing protein 4, is involved in the complement system and it is encoded by the C5 gene in human. Complement C5 is cleaved into C5a and C5b. C5a plays an important role in chemotaxis and C5b forms the first part of the complement membrane attack complex. Complement C5 is the fifth component of complement, which plays an important role in inflammatory and cell killing processes. This protein is composed of alpha and beta polypeptide chains that are linked by a disulfide bridge. An activation peptide, C5a, which is an anaphylatoxin that possesses potent spasmogenic and chemotactic activity, is derived from the alpha polypeptide via cleavage with a convertase. The C5b macromolecular cleavage product can form a complex with the C6 complement component, and this complex is the basis for formation of the membrane attack complex, which includes additional complement components.