Polyamine and thiol metabolism in Trypanosoma granulosum: similarities with Trypanosoma cruzi

Concentrations of free polyamines were investigated in Trypanosoma granulosum cultured in a semidefined medium containing traces of polyamines. Spermidine content peaked in early logarithmic growth while putrescine was not detectable. Unlike African trypanosomes and Leishmania, spermine was measured at equivalent amounts to spermidine in mid to late logarithmic stage cells. Addition of d,l-alpha-difluoromethylornithine to cultures did not decrease polyamine content nor was ornithine decarboxylase activity detected. In contrast, incubation of parasites with tritiated putrescine showed rapid uptake and subsequent conversion to spermidine and spermine. At late logarithmic growth, parasites contained glutathione (77% of total sulphydryl groups) and ovothiol A as major low molecular mass thiols with glutathionylpolyamine conjugates undetectable. However, the addition of exogenous putrescine elevated trypanothione and glutathionylspermidine content to 48% of total sulphydryl groups. Correspondingly, the addition of exogenous cadaverine increased homotrypanothione content. This first report of polyamines and low molecular mass thiols in Trypanosoma granulosum indicates intriguing similarities with the metabolism of the human pathogen Trypanosoma cruzi.