ACE, found in lungs, blood vessels, and mucosa wall, is an important component of the renin-angiotensin system, implicated in the regulation of arterial tension, blood volume, and the balance of electrolytes. Renin, an aspartic proteinase of the renin-angiotensin system(RAS), hydrolyzes angiotensinogen, releasing angiotensin I, a decapeptide. Then, ACE hydrolyzes angiotensin I to angiotensin II, an octapeptide, by removing His-Leu from its C-terminal. Angiotensin II is a vasoconstrictor an inhibitor of bradykinin(a vasodilator). This hormone increases the production of aldosterone, which affects ion retention and the excretion of fluids and therefore causes hypertension. Angiotensin II directly influences blood pressure. consequently, any peptide that has an inhibitory action on ACE can be considered an antihypertensive peptide.