The chitinase system from Trichomonas vaginalis as a potential target for antimicrobial therapy of urogenital trichomoniasis

Chitinolytic activities in Trichomonas vaginalis membrane extracts were assessed by assays of three enzyme systems: N-acetyl-β- -hexosaminidase (NAHase), chitobiosidase and chitotriosidase. N-acetyl-β- -hexosaminidase was the enzyme that showed the highest specific activity. After successive subcutaneous inoculations into mice and parasite recovery in culture, the enzyme activities increased significantly with the number of inoculations for up to eight passages. In addition, enzyme activities were maximum at the logarithmic phase of growth. Glycol chitin, a chitinase substrate, enhanced all chitinolytic activities by about 30% and a clear-cut correlation is shown between the capacity for erythrocyte lysis by parasites and NAHase expression. Chitobiosidase and chitotriosidase activities were both inhibited at 58% and 100%, respectively, by allosamidine, a chitinase inhibitor used at 3 μM, whereas NAHase activity was not affected. Seven putative NAHase inhibitors (compounds n, 1–7), ureido and thioureido derivatives of 2-amino-2-deoxy- -glucose were evaluated and five of them had Ki values in the range 30–70 μM. The most active compound (compound 6) was functionally competitive with respect to the substrate with a Ki value of 30 μM. The IC50 values of the most active compounds on T. vaginalis were in the range 62–85 μM. These results indicate that chitinases of T. vaginalis are involved in pathogenicity and they could be an interesting target for drugs since chitinase inhibitors also inhibit parasite growth.