A Mathematical Model for the Influence of Anionic Effectors on the Phosphofructokinase from Rat Erythrocytes

The influence of the positive effectors AMP, sulphate, glucose 1,6‐bisphosphate and the negative effector 2,3‐bisphoglycerate on rat erythrocyte phosphofructokinase has been investigated. The kinetic data have been fitted to the Monod‐Wyman‐Changeux model as well as to a model based on a closed association‐dissociation equilibrium. The application of the fitting procedure yields for both models a good correspondence between theoretical and experimental data and equal results with respect to the action of the effectors on the enzyme. The corresponding dissociation constants for the binding of the positive effectors to the active state are: AMP 35 μM, sulphate 0.43 mM and glucose 1,6‐bisphosphate 15 μM. 2,3‐Bisphosphoglycerate as an inhibitor stabilizes the inactive state (dissociation constant: 1.4 mM).A preliminary discrimination between the Monod‐Wyman‐Changeux model and the association‐dissociation model has been attempted.