Stimulation of Trypanosoma brucei pyruvate kinase by fructose 2,6‐bisphosphate

The activity of pyruvate kinase present in a crude extract of the bloodstream form of Trypanosoma brucei was greatly increased by fructose 2,6‐bisphosphate, which converted the saturation curve for phospho en olpyruvate from a sigmoid into a hyperbola with no change in V . Phosphate and arsenate had an effect opposite to that of fructose 2,6‐bisphosphate and the apparent K a for fructose 2,6‐bisphosphate was shifted from 75 nM to 1.5 μM by the presence of 5 mM phosphate. Fructose 1,6‐bisphosphate had effects similar to those of fructose 2,6‐bisphosphate but at approximately 4000‐fold higher concentrations. Pyruvate kinases of Crithidia luciliae and of Leishmania major , two trypanosomatids which are like T. brucei in containing glycosomes, were also stimulated by fructose 2,6‐bisphosphate and inhibited by phosphate.