Quantification of Angiotensin-Converting Enzyme (ACE) Activity

Angiotensin-converting enzyme (ACE) is a dipeptidyl carboxypeptidase (EC 3.4.15.1) whose physiologic action is the conversion of AI to AII, and as such, it plays an important role in the regulation of blood pressure and fluid balance. ACE has been localized to endothelial cells throughout the body and epithelial cells in gut and kidney. It exists both as a membrane-bound enzyme and in a freely soluble form in plasma. The importance of the membrane-bound form is underscored by the recently described local renin-angiotensin system (RAS) in various organs, including heart, blood vessels, and kidney (1 ). In the heart and vascular smooth muscle, the local RAS is believed to play an important role in hypertrophy and remodeling. Accordingly, accurate and reliable methods for measurement of tissue (i.e., membrane bound) ACE activity are important, as well as soluble ACE activity.