Compared recognition of di- and trisulfide substrates by glutathione and trypanothione reductases

Trypanothione trisulfide was synthesized according to two strategies. It was found to be recognized and reduced by trypanothione reductase as the natural disulfide substrate. At the difference with the mechanism observed for the reduction of glutathione trisulfide by glutathione reductase, the intermediate trypanothione persulfide was rapidly reduced. The enzymatic reduction of another trisulfide derived from an alternative substrate of trypanothione reductase was also studied. The structure of the trisulfide bridge of the substrate (intra- or intermolecular) appeared to be a determining factor in the enzymatic reduction pattern. Moreover, in the case of the alternative substrate of trypanothione reductase, differences of kinetics appeared for the first time between a di- and a trisulfide species. All kinetic parameters are given.