CITRATE INHIBITION OF RAT-KIDNEY CORTEX PHOSPHOFRUCTOKINASE

The regulatory properties of citrate on the activity of phosphofructok inase (PFK) purified from rat-kidney cortex has been studied. Citrate produces increases in the K-0.5 for Fru-6-P and in the Hill coefficien t as well as a decrease in the V-max of the reaction without affecting the kinetic parameters for ATP as substrate. ATP potentiates synergis tically the effects of citrate as an inhibitor of the enzyme. Fru-2,6- P-2 and AMP at concentrations equal to K-a were not able to completely prevent citrate inhibition of the enzyme. Physiological concentration s of ATP and citrate produce a strong inhibition of renal PFK suggesti ng that may participate in the control of glycolysis in vivo.