Angiotensin I is converted to angiotensin II (AII) through removal of two C-terminal residues by the enzyme angiotensin-converting enzyme (ACE), primarily through ACE within the lung (but also present in endothelial cells, kidney epithelial cells, and the brain). Angiotensin II acts on the CNS to increase ADH production, and also acts on venous and arterial vessels' smooth muscle to cause vasoconstriction. Angiotensin II also increases Aldosterone secretion, therefore, it acts as an endocrine, autocrine/paracrine, and intracrine hormone.
Angiotensin II is degraded to angiotensin III by angiotensinases located in red blood cells and the vascular beds of most tissues. It has a half-life in circulation of around 30 seconds, whereas, in tissue, it may be as long as 15–30 minutes.