Abstract
Angiotensin converting enzyme-2 (ACE2) is a recently described homologue of the vasoactive peptidase, angiotensin converting enzyme (ACE). Like ACE, ACE2 is an integral (type I) membrane zinc metallopeptidase, which exists as an ectoenzyme. ACE2 is less widely distributed than ACE in the body, being expressed at highest concentrations in the heart, kidney and testis. ACE2 also differs from ACE in its substrate specificity, functioning exclusively as a carboxypeptidase rather than a peptidyl dipeptidase. A key role for ACE2 appears to be emerging in the conversion of angiotensin II to angiotensin (1-7), allowing it to act as a counter-balance to the actions of ACE. ACE2 has been localised to the endothelial and epithelial cells of the heart and kidney where it may have a role at the cell surface in hydrolysing bioactive peptides such as angiotensin II present in the circulation. A role for ACE2 in the metabolism of other biologically active peptides also needs to be considered. ACE2 also serendipitously appears to act as a receptor for the severe acute respiratory syndrome (SARS) coronavirus. Studies using ace2 (-/-) mice, and other emerging studies in vivo and in vitro, have revealed that ACE2 has important functions in cardiac regulation and diabetes. Together with its role as a SARS receptor, ACE2 is therefore likely to be an important therapeutic target in a diverse range of disease states.