Proteinase 3 is one of the serine proteinases localized in azurophil granules of polymorphonuclear leukocytes. It has been identified as the autoantigen of Wegener granulomatosis, a systemic vasculitis complicated by melomonocyte proliferation. It exhibits proteolytic activity towards a range of substrates. It is physiologically inhibited by alpha1-antitrypsin. The protein has been described as having antibiotic and growth-promoting properties and causing emphysema when administered by tracheal insufflation.
