Trichomonas vaginalis, Tritrichomonas foetus, and Trichomitus batrachorum: comparative proteolytic activity

At least four proteolytic activities were detected in the lysates of each of Trichomonas vaginalis, Tritrichomonas foetus, and Trichomitus batrachorum. These were HPAase, a dithiothreitol-dependent activity on hide powder azure; AZCase, a dithiothreitol-dependent activity on azocasein; and two distinct activities towards peptide nitroanilide derivatives--one was optimally active at pH 7 and stimulated by dithiothreitol; the other had no dithiothreitol requirement and was highly active at pH 5. HPAase and AZCase were active over a broad pH range. Overall, with respect to these four activities, T. batrachorum and T. vaginalis were quite similar. In contrast, T. vaginalis and T. foetus differed from one another in several respects, notably the level of HPAase activity and the properties of the dithiothreitol-independent activity. Multiple bands of proteinase activity were demonstrated with each species after electrophoresis of parasite extracts on polyacrylamide gels containing denatured haemoglobin. They appeared optimally at acid pH and in the presence of dithiothreitol. The proteinase band patterns of T. foetus were similarly complex (at least six bands), whereas T. batrachorum gave a much simpler pattern (three bands). The sensitivities to proteinase inhibitors suggested that all the activities were due to cysteine proteinases. The results show that there are some similarities in the proteolytic activities of all three trichomonad species, and that the two parasites of the urinogenital tracts of mammals possess additional features in common.