[An endogenous activator of angiotensin-converting enzyme]

An endogenous activator of the angiotensin-converting enzyme (ACE), unknown earlier, was detected in freshly prepared human neutrophils. Supernatants of the neutrophil suspension produced a 1.6-2-fold activation of the ACE isolated from bovine kidney cortex. The ACE activating effect of these supernatants correlated with concentration of neutrophils in the initial suspension. The activator did not penetrate through membranes of Centricon-30. This activator was also found in blood serum of patients with hereditary deficiency of the complement CI-esterase inhibitor. The neutrophil-released ACE activator is likely to be involved in the modulation of inflammatory responses.