Trypanothione dependent peroxide metabolism in Crithidia fasciculata and Trypanosoma brucei

A trypanothione-dependent peroxidase activity has been identified in the insect trypanosomatid Crithidia fasciculata and in the mammalian trypanosome Trypanosoma brucei. Using organic hydroperoxides as oxidant, specific peroxidase activities in these organisms are 5.0 and 1.0 nmol min-1 (10(8) cells)-1 respectively. The T. brucei peroxidase had an activity of 0.4 nmol min-1 (10(8) cells)-1 using hydrogen peroxide as oxidant. The enzyme is specific for the N1,N8-bis(glutathionyl)spermidine conjugate (dihydro-trypanothione); N1-mono-glutathionylspermidine is not a substrate. Experiments to demonstrate that this parasite peroxidase may contain selenium were inconclusive. However, bloodstream T. brucei can incorporate radiolabelled selenite into proteins.