PURIFICATION AND CHARACTERIZATION OF A TRYPANOTHIONE-GLUTATHIONE THIOLTRANSFERASE FROM TRYPANOSOMA-CRUZI

Although trypanothione [T(S)(2)] is the major thiol component in trypa nosomatidae, significant amounts of glutathione are present in Trypano soma cruzi. This could be explained by the existence of enzymes using glutathione or both glutathione and T(S)(2) as cofactors. To assess th ese hypotheses, a cytosolic fraction of T. cruzi epimastigotes was sub jected to affinity chromatography columns using as ligands either S-he xylglutathione or a nonreducible analogue of trypanothione disulphide, A similar protein of 52 kDa was eluted in both cases, Its partial ami no acid sequence indicated that it was identical with the protein enco ded by the TcAc2 cDNA previously described [Schoneck, Plumas-Marty, Ta ibi et al. (1994) Biol, Cell 80, 1-10]. This protein showed no signifi cant glutathione transferase activity but surprisingly catalysed the t hiol-disulphide exchange between dihydrotrypanothione and glutathione disulphide. The kinetic parameters were in the same range as those det ermined for trypanothione reductase toward its natural substrate. This trypanothione-glutathione thioltransferase provides a new target for a specific chemotherapy against Chagas' disease and may constitute a l ink between the glutathione-based metabolism of the host and the trypa nothione-based metabolism of the parasite.