Description_x000D_ General description_x000D_ The angiotensin-converting enzyme (ACE) is a dipeptidyl-carboxypeptidase which exists in somatic and testicular isoforms with zinc binding motif HEXXH in their active site. ACE regulates blood pressure through renin-angiotensin system. ACE elevates blood pressure by converting angiotensin I to a key vasoconstrictor angiotensin II and inhibiting a potent vasodilator bradykinin. Inhibition of ACE is a targeted therapeutic strategy for high blood pressure. Several ACE synthetic inhibitory peptides available for clinical use include captopril, enalapril and lisinopril. Currently, developing inhibitory peptides from natural food sources, or phenolic compounds from plant sources to inhibit ACE is underway. ACE plays a critical role in fertilization by releasing the proteins anchored to glycosylphosphatidylinositol (GPI) in sperm membrane._x000D_ Application_x000D_ Angiotensin converting enzyme from rabbit lung has been used:_x000D_ • for measuring inhibitory effect of egg white protein hydrolysates on ACE activity by high performance liquid chromatography (HPLC)_x000D_ • to measure the ACE inhibition by litchi pericarp and cooked chicken breast using hippuryl-L-histidyl-L-leucine (HHL) as substrate by reverse phase-HPLC (RP-HPLC)3 and HPLC respectively_x000D_ • in releasing GPI anchored protein in vitro in few cell lines like HeLa, HEK293 and in vivo in mice sperm._x000D_ Biochem/physiol Actions_x000D_ Removes C-terminal dipeptides from susceptible substrates, e.g., angiotensin I and bradykinin._x000D_ Quality_x000D_ May contain traces of sodium chloride._x000D_ Unit Definition_x000D_ One unit will produce 1.0 μmole of hippuric acid from Hippuryl-His-Leu per min in 50 mM HEPES and 300 mM NaCl at pH 8.3 at 37 °C.