Intracellular Distribution of Carbon Dioxide-fixing Enzymes in Trypanosoma cruzi and Crithidia fasciculata

Abstract
The intracellular distribution of phosphoenolpyruvate carboxykinase (EC 4.1.1.49) and NADP-linked malic enzyme (EC 1.1.1.40) activity in epimastigotes of T. cruzi (Tulahuen strain) and in C. fasciculata was studied by 2 procedures: subcellular fractionation by differential centrifugation of homogenates obtained by breaking the cells in a mortar; selective disruption of cellular membranes by digitonin treatment. Phosphoenolpyruvate carboxykinase is particulate in both organisms, as is 1 of the 2 forms of malic enzyme present in T. cruzi (malic enzyme I), whereas the other malic enzyme of T. cruzi (malic enzyme II) and the single malic enzyme of C. fasciculata are in the cytosol.