A recently discovered homologue of the angiotensin-converting enzyme, ACE2, insensitive to ACE inhibitors, was found in rodents and humans. ACE2 is expressed mainly in the vasculature, heart and kidney. ACE2 removes a single amino acid of the carboxy terminal of peptides. In the renin-angiotensin-aldosterone system (RAAS), it is responsible for the conversion of angiotensin I (Ang I) and angiotensin II (Ang II) to Ang 1-9 and Ang 1-7, respectively. While ACE forms Ang II, a potent vasoconstrictor, ACE2 degrades this peptide to form Ang 1-7 which has an opposite action. Therefore, ACE2 counteracts ACE in the balance of vasopressor/vasodilator as well as heart and kidney function. The importance of ACE2 in physiological and pathophysiological conditions is unclear and is currently being studied.
