Regulation of rat-renal cortex phosphofructokinase activity by pH

The activity of phosphofructokinase purified from rat kidney cortex has been assayed at two different pH values. At pH 7 the enzyme showed cooperativity for the binding of fructose 6-phosphate (Fru-6-P) and a strong allosteric inhibition by ATP. When the assays were done at pH 8 hyperbolic kinetics were observed for both substrates, a smaller inhibition by ATP was observed and the Vmax for ATP and for Fru-6-P was higher than at pH 7. A sequential reaction mechanism was inferred. Results are discussed in terms of the importance of a reduced hexose-phosphate cycling rate during metabolic acidosis induced by exercise.