Angiotensin-converting enzyme (ACE) is an important protein in the body that helps regulate blood pressure. It converts a hormone called angiotensin I into angiotensin II, which narrows blood vessels and increases blood pressure. This process is part of the renin-angiotensin system, a key mechanism for maintaining cardiovascular health. ACE is found mainly in the lungs and kidneys. It plays a crucial role in fluid balance and blood pressure control. Medications that inhibit ACE, known as ACE inhibitors, are commonly prescribed to treat high blood pressure and heart failure by preventing the formation of angiotensin II.