angiotensin-converting enzyme

Angiotensin-converting enzyme, usually called ACE, is the molecular “scissors” that finishes building the body’s strongest pressure-raising hormone. It takes an inactive precursor and snips off two amino acids to switch it on.

Specifically, ACE converts angiotensin I (which has little activity on its own) into angiotensin II (which is potent) by removing a pair of amino acids from one end. ACE is found in large amounts on the inner lining of blood vessels, especially in the lungs, so blood passing through the lungs is rapidly converted. The same enzyme also breaks down bradykinin, a peptide that widens vessels, so ACE both makes a vasoconstrictor and destroys a vasodilator — a double push toward higher pressure.

ACE inhibitors are a cornerstone of treating high blood pressure, heart failure, and kidney disease in diabetes; drug names typically end in “-pril.” A well-known side effect, a dry cough, comes precisely because blocking ACE lets bradykinin build up. This shows that the enzyme’s biology and its drugs are two sides of the same story.