Pathways leading to the generation of bradykinin. C1 inhibitor (C1INH), in red, blocks the conversion of HMW kininogen to bradykinin while the effect of ACE inhibitors is to impede the breakdown of bradykinin. High molecular weight kininogen (HMW kininogen), bradykinin B2 receptor, angiotensin converting enzyme (ACE), angiotensin converting enzyme inhibitors (ACE inhibitors).