ESI MS Studies of T. Brucei Trypanothione Reductase and its Reactions With Selected Metal Compounds

Trypanothione reductase from Trypanosoma brucei (TbTR) is a key enzyme of the parasite responsible for human African trypanosomiasis. TbTR catalyzes the reduction of trypanothione, an antioxidant dithiol that protects trypanosomatid parasites from oxidative stress induced by the mammalian host as a defense system. TbTR is considered an attractive target for the development of novel anti-parasitic drugs because it is essential for parasite survival and has no close homologues in humans. Previous studies have shown that metal compounds can act as potent inhibitors of trypanothione reductase and of related enzymes and may be considered for disease treatment. To better understand the molecular basis of such inhibition, we report the study of the interactions of a small group of metal compounds with TbTR, analyzed by ESI MS measurements. This technique allows direct visualization of the enzyme in solution and the detection and characterization of the metal binding process. Accordingly, TbTR was reacted with a panel of metal compounds including thimerosal, auranofin, its halogen analogues, and bismuth acetate. ESI MS results provide a detailed description of the interactions taking place for each metal compound tested. The implications of these results for the development of novel metal-based compounds as potential anti-trypanosomal agents are discussed.