Complex kinetics of human leukocyte and platelet pyruvate kinases

In the presence of SH group protectors, human leukocyte and platelet pyruvate kinases demonstrate biphasic kinetics with respect to the phosphoenolpyruvate substrate. SH group oxidation by oxidized glutathione reveals positive cooperativity kinetics for purified preparations of leukocyte and platelet pyruvate kinases. Complete reversal of the phenomenon may be obtained by incubation for several hours in dithiothreitol. This communication illustrates the existing relationships between enzyme conformation, the redox state of the SH groups, and the observed kinetics.