Intracellular distribution of CO2-fixing enzymes in Trypanosoma cruzi and Crithidia fasciculata
Cannata, J.J.; Docampo, R.; Valle, E.; Franke de Cazzulo, B.M.; Cazzulo, J.J.
Medicina 40(Suppl): 145-153
1980
ISSN/ISBN: 0025-7680 PMID: 6779078 Document Number: 165951
The distribution of CO2 fixing enzymes and of citrate synthase in supernatant and particulate fractions of homogenates of Trypanosoma cruzi and Crithidia fasciculata were studied. In T. cruzi, 92.4% of the malic enzyme activity was present in the supernatant whereas 69% of the phosphoenolpyruvate carboxykinase activity was in the particulate fraction, as was 23.4% of the citrate synthase. The corresponding values for C. fasciculata were over 90%, nearly 100% and 38.3%. These experiments suggested extensive fragmentation of the mitochondrion, leading to considerable leaking of citrate synthase to the supernatant. Malic enzyme activity was extracted from whole cells at concentrations of digitonin considerably lower (0.125 to 0.25 mg digitonin/mg cellular protein) than those required to extract citrate synthase (1.3 to 1.5 mg/mg protein), both in the case of T. cruzi and C. fasciculata. The results suggest that most of the malic enzyme activity is located in the cytosol.