Reversible Inactivation of Rabbit Liver Fructose 1,6-Diphosphatase by Adenosine Triphosphate and Adenosine Diphosphate

Abstract

Abstract ATP, ADP, and other nucleoside pyrophosphates converted homogeneous rabbit liver fructose 1,6-diphosphatase into a conformer with low catalytic activity, and altered the nature of the allosteric inhibition by AMP from sigmoidal to hyperbolic. This transition was both prevented and reversed by 3-phosphoglycerate or EDTA. Higher concentrations of inorganic phosphate and certain polycarboxylic acids and phosphate esters had similar effects. Two phosphonic acid analogues of ATP,β,γ-methylene adenosine 5'-triphosphate and α,β-methylene adenosine 5'-triphosphate, were found to inactivate the enzyme very specifically at much lower nucleotide concentrations. Mg2+ was required both for ATP inactivation to occur and for the prevention of this process by 3-phosphoglycerate. On the other hand, low concentrations of substrate markedly slowed down the interconversions in either direction.