Characterization of angiotensin I-converting enzyme activity in the freshwater turtle, Amyda japonica

1. Angiotensin I-Converting Enzyme (ACE) activity has been characterized in the freshwater turtle, Amyda japonica. 2. Peak activity of ACE in plasma from the freshwater turtle was shown at pH 9.0, which was more alkaline compared to that of mammals. 3. Chloride requirements for the optimal ACE activity were different from species. 4. ACE inhibitors, EDTA, teprotide (SQ 20,881), Captopril (SQ 14,225) showed dose-dependent inhibitions of ACE activity in plasma from the freshwater turtle as well as mammals. 5. ACE activity was found in several different tissues with a different activity showing the highest activity in kidney homogenate from the freshwater turtle, Amyda japonica.