BINDING OF ADENOSINE 5'-MONOPHOSPHATE AND SUBSTRATE BY RABBIT LIVER FRUCTOSE 1,6-DIPHOSPHATASE

The binding of adenosine 5′-monophosphate and fructose 1,6-diphosphate by rabbit liver fructose 1,6-diphosphatase has been studied by the technique of gel filtration. Four binding sites for each ligand per enzyme molecule were estimated from Scatchard plots. In the presence of substrate and absence of divalent cation, the tightness of adenosine S′-monophosphate binding to the enzyme was greatly increased and positive cooperative interaction was observed among the adenosine 5′-monophosphate binding sites. No cooperative interaction was detectable among the substrate binding sites. At pH 7.3 and 3°, the respective primary association constants were estimated to be 3.2 × 105 M-1 for adenosine 5′-monophosphate and 1.6 × 105 M-1 for fructose 1,6-diphosphate. © 1969, American Chemical Society. All rights reserved.