Kinetic Studies of Thiosemicarbazone Inhibitors of Cruzain, a Validated Target of Cruzain

Chagas’ disease is caused by the flagellate protozoan Trypanosoma cruzi. As determined by the World Health Organization, effective therapeutic medications are needed for the treatment of Chagas’ disease. Cruzain, a powerful cysteine protease involved in cell invasion, immune evasion, and metabolism of the T. cruzi parasite, is a validated target for the disease. A number of thiosemicarbazone derivatives are inhibitors of cruzain. In this study, the kinetic mechanism of a potent thiosemicarbazone inhibitor of cruzain was investigated. A microplate reader using a 96-well plate format was used to perform fluorometric assays. Progress curves provided evidence that this thiosemicarbazone compound is a time-dependent inhibitor of cruzain. This was a collaborative study between the Trawick and Pinney groups at Baylor University.