The interaction of purified enolase with its activating metal ions

Abstract

1. 1. The substrate kinetics of the enolase reaction was studied. High substrate concentrations were shown to have an inhibitory effect. Possible reaction mechanisms were discussed. 2. 2. The influence of the concentration of Mn ++ and Zn ++ on enolase activity was investigated. The activity-concentration curves were found to go through a maximum. An equation describing this effect was derived by assuming that the metal ions interact with two sets of sites on the enolase molecule, one leading to activation and the other to inhibition. 3. 3. The maximum activity with a given concentration of enzyme was not the same for the different metal ions. It was suggested that the ionic radius of a given metal ion is the main property determining its activating power. 4. 4. The interaction of enolase with Mn ++ and Zn ++ was studied by equilibrium dialysis. By comparison with the activation experiments, it was concluded that the activation involves the binding of one single metal ion per molecule of enzyme. Additional metal ions were found to be bound, but this resulted in inhibition.