Angiotensin I converting enzyme 2 (ACE 2) is an exopeptidase that catalyses the conversion of angiotensin I to the nonapeptide angiotensin[1-9], or the conversion of angiotensin II to angiotensin 1-7. ACE 2 has direct effects on cardiac function, and is expressed predominantly in vascular endothelial cells of the heart and the kidneys.