Species differences in the angiotensin converting enzyme activity of mammalian serum

Angiotensin converting enzyme (ACE; EC 3. 4. 15. 1) activities were compared in the serum of various mammals. Cattle, human, monkey, and swine serum showed enzyme levels from 3.7 to 67 mU/ml. Relatively high enzyme activity was observed in rodents, the rat (Wistar) and mouse (BALB/c) showing levels of 93 +/- 7 and 1052 +/- 165 mU/ml, respectively. Among the mammalian sera examined, that of the guinea pig contained the highest ACE level, 2262 +/- 574 mU/ml. No age-related difference in enzyme activity was observed in 10-day-old to 1-year-old guinea pigs.