The Angiotensin Converting Enzyme (ACE) test is performed to measure the level of the Angiotensin Converting Enzyme (ACE) in the blood. ACE is an important enzyme in the body that is involved in the renin-angiotensin system, which helps regulate blood pressure and water balance in the body. ACE converts angiotensin I into angiotensin II, a compound that helps constrict blood vessels and raise blood pressure.