Leishmania donovani and L. braziliensis: Function of pyruvate kinase

Regulatory properties of pyruvate kinase (EC 2.7.1.40) from Leishmania donovani and Leishmania braziliensis were determined in relation to the enzyme's regulation of glycolysis. L. donovani enzyme responded to its substrate, phosphoenolpyruvate, in a sigmoidal manner while L. braziliensis responded hyperbolically. No heterotropic modifiers, with the exception of hydrogen ion, have been found to influence the activity of this enzyme. Activation by hydrogen ion does not appear to be significant physiologically. Enzymes from these organisms were found to differ somewhat in their kinetics from that reported for Crithidia fasciculata, but the regulatory functions are similar. The conversion of phosphoenolpyruvate to oxaloacetate in these Leishmania spp. appears to involve pyruvate kinase and pyruvate carboxylase. In C. fasciculata phosphoenolpyruvate carboxykinase appears to be more important.