Respiratory control in mitochondria from Trypanosoma cruzi.

Phosphorylating mitochondrial membranes were obtained from Trypanosoma cruzi culture (epimastigote) forms. Using ADP as phosphate acceptor and succinate, sn-glycerol-3-phosphate, L-malate or ascorbate plus tetramethyl-p-phenylenediamine (TMPD) as oxidizable substrates, energy coupling sites II and III were detected, with respiratory control values in the range of 2.8-2.0. Carbonyl cyanide m-chlorophenylhydrazone and sonication uncoupled the respiratory control mechanism. Antimycin and cyanide partially inhibited succinate, sn-glycerol-3-phosphate and L-malate oxidation, while cyanide totally inhibited ascorbate + TMPD oxidation by the mitochondrial preparation. Succinate oxidation was inhibited by malonate and oxalacetate, but this latter was only effective with sonicated mitochondria. At variance with other substrates, NADH oxidation was not controlled by ADP concentration or inhibited by antimycin or cyanide. Rotenone failed to inhibit electron transfer in T. cruzi mitochondria.