REGULATION OF RAT RENAL-CORTEX PHOSPHOFRUCTOKINASE ACTIVITY BY PH

The activity of phosphofructokinase purified from rat kidney cortex ha s been assayed at two different pH values. At pH 7 the enzyme showed c ooperativity for the binding of fructose 6-phosphate (Fru-6-P) and a s trong allosteric inhibition by ATP. When the assays were done at pH 8 hyperbolic kinetics were observed for both substrates, a smaller inhib ition by ATP was observed and the V-max for ATP and for Fru-6-P was hi gher than at pH 7. A sequential reaction mechanism was inferred. Resul ts are discussed in terms of the importance of a reduced hexose-phosph ate cycling rate during metabolic acidosis induced by exercise.