Elution profiles and molecular weights of placental cystine aminopeptidase in animals

Gel filtration was performed for cystine aminopeptidase (CAP) [EC 3.4.11.3] on full term placental extracts from human, cynomolgus monkey, dog, goat, pig and horse. The enzymatic profiles of CAP were examined and compared with that of CAP in pregnancy plasma on the basis of inhibitory effects. Elution profiles of placental extracts exhibited 2 CAP activity peaks in human and pig, 3 peaks in cynomolgus monkey, dog and goat, and 4 peaks in horse. The molecular weights of placental CAP that showed identical inhibitory effects to that of pregnancy plasma CAP were estimated to be approximately 325,000 in human, 350,000 in the cynomolgus monkey, 140,000 in the dog, 140,000 in the goat, 128,000 in the pig, and 115,000 in the horse. These molecular weights tended to decrease in accordance with the increase of barrier layers present between maternal blood and placental syncytiotrophoblasts in which CAP is synthesized.