Another functional similarity between P. gingivalis and tumor cells, which produce either complement inhibitors or complement components, is the fact that P. gingivalis not only possesses the proteolytic machinery to generate C5a but also expresses a unique enzyme, peptidyl arginine deiminase (PPAD), which can citrullinate the C-terminal arginine in C5a, a modification that results in substantial loss of anaphylatoxin chemotactic activity (79). The gene discussed is C5; the disease is neoplasm.