[Existence of 2 sites of oxidative phosphorylation in Trypanosoma cruzi]

Phosphorylating mitochondrial preparations were obtained from T. cruzi culture (epimastigote) forms by grinding the cells with glass - beads and differential centrifugation. Using ADP as phosphate acceptor and succinate, L-malate or ascorbate + tetramethyl-p-phenylenediamine (TMPD) as oxidizable substrates, the respiratory control (R.C.) values were (mean +/- S.D.; n = 4, in parenthesis, the substrate): 2.8 +/- 0.10 (succinate): 2.3 +/- 0.13 (L-malate) and 2.0 +/- 0.12 (ascorbate + TMPD). The ADP:O values were 1.68 +/- 0.08, 1.42 +/- 0.08 and 0.66 +/- 0.66 +/- 0.12, respectively. The uncoupler CCCP stimulated substrate oxidation somewhat more than ADP. Succinate oxidation was by malonate and also by oxaloacetate but the latter was effective only after sonicating the mitochondrial preparation. The mitochondrial membranes oxidized also NADH but this oxidation was not subjected to control by the phosphate acceptor. Our results support the existence of two energy-conserving sites in T. cruzi respiratory chain (sites 2 and 3) and confirm previous observations by Stoppani et al. (Mol. Biochem. Parasitol. 2:3-21, 1980) with intact epimastigotes.