Comparison of vaginal aminopeptidase enzymatic activities in various animals and in humans

The specific enzymatic activity of four different aminopeptidases (aminopeptidase N, leucine aminopeptidase, aminopeptidase A and aminopeptidase B) in vaginal homogenates from rabbit, rat, guinea-pig, sheep and humans was compared. The purpose of the study was to find an appropriate animal model that can be used in degradation studies of protein and peptide drugs. Different substrates were used as the relative specific substrates for the determination of aminopeptidase enzymatic activity: 4-methoxy-2-naphthylamide of L-alanine for aminopepticlase N, 4-methoxy-2-naphthylamide of L-leucine for leucine aminopepticlase, 4-methoxy-2-naphthylamide of L-glutamic acid for aminopeptidase A and 4-methoxy-2-naphthylamide of L-arginine for aminopepticlase B. The vaginal aminopepticlase enzymatic activity of different species was determined spectrofluorometrically. The inhibition of aminopepticlase activity in the presence of bestatin and puromycin inhibitors was also investigated. The results showed the presence of aminopepticlase enzymatic activity in all vaginal homogenates in the order: sheep > guinea-pig > rabbit greater than or equal to human greater than or equal to rat. Based on the results of the hydrolysis and inhibition of the 4-methoxy-2-naphthylamide substrates, it was difficult to have an exact decision on the aminopepticlase type in the vaginal homogenates from the species studied. It was found that the aminopepticlase activity in rat, rabbit and humans was not statistically different. Therefore, we suggest that rats and rabbits could be used as model animals for vaginal enzymatic activity studies and for determination of the degradation of protein and peptide drugs in the vagina.