Peptidyl-dipeptidase A, also known as angiotensin-converting enzyme (ACE), is a membrane-bound carboxypeptidase that converts the inactive decapeptide angiotensin I to the potent vasoconstrictor octapeptide angiotensin II, and inactivates the vasodilator bradykinin. This enzyme plays a crucial role in the regulation of blood pressure and fluid-electrolyte balance.