[Properties of 6-phosphogluconate dehydrogenase from livers of healthy and neoplastic rats].

The steady state kinetics of 6-phosphogluconate dehydrogenase from the liver of healthy and neoplastic rats (sarcoma S-45) were studied. The kinetic measurements were carried out at 18 degrees in a glycyl-glycine buffer, pH 7.6. The kinetic analysis of the purified enzyme preparations included determination of initial rates of the reaction and calculation of the kinetic plots of the reaction according to Cleland and Eisenthal and Kornish-Bouden. A comparison of the kinetic data for all experimental series allowed to postulate the absence of damages in the total mechanism of the reaction in case of neoplastic rats; however, the rate constants for individual steps of this process are changed as can be evidenced from the Km values for the substrates. The normalizing effect of hydroxythiamine injected parenterally into neoplastic animals on the kinetic parameters of 6-phosphogluconate dehydrogenase was observed.