Angiotensin I is converted to angiotensin II through removal of two terminal residues by the enzyme Angiotensin-converting enzyme (ACE, or kinase), which is found predominantly in the capillaries of the lung. ACE is actually found all over the body, but has its highest density in the lung due to the high density of capillary beds there. Angiotensin II acts as an endocrine, autocrine/paracrine, and intracrine hormone.ACE is a target for inactivation by ACE inhibitor drugs, which decrease the rate of angiotensin II production.

Angiotensin II increases blood pressure by stimulating the Gq protein in vascular smooth muscle cells . ACE inhibitor drugs are major drugs against hypertension.Other cleavage products of ACE, 7 or 9 amino acids long, are also known; they have differential affinity for angiotensin receptors, although their exact role is still unclear.