Native human C9 is a naturally glycosylated (7.8%) protein composed of a single polypeptide chain. The molecular weight is 71,000 Da. C9 binds to the C5b-8 complex and forms the mature membrane attack complex (MAC) on cell membranes. Each pathway of complement activation generates proteolytic enzyme complexes which are bound to the target surface. These enzymes cleave a peptide bond in the larger alpha chain of C5 releasing the anaphylatoxin C5a and activating C5b. Description: Human serum/plasma. Synonyms: C9 protein.