Effect of chloride and diamide on angiotensin converting enzyme from sheep testis and epididymis

Effect of chloride and diamide on testicular and epididymal angiotensin converting enzyme (ACE) activity was investigated using Hip-His-Leu as substrate in sheep. The chloride ions functioned as ACE activators, however, there was no linear correlation between the two. The optimum chloride concentrations were 500 mM for epididymal ACE and 900-1100 mM for testicular ACE. Further, optimum chloride concentration increased ACE activity of testis and epididymis 25.40- folds and 12.84- folds respectively of the activities at physiological chloride concentration. The differences found in the effect of chloride on testicular and epididymal ACE activity suggest dissimilar three dimensional structure of ACE in these tissues. Increased testicular and epididymal ACE activity on diamide pretreatment indicates that tissue oxidation may affect ACE activity.