The influence of divalent cations on allosteric behaviour of muscle pyruvate kinase from the sea mussel Mytilus edulis L.

Abstract

1. 1. Pyruvate kinase of the adductor muscle of the sea mussel displays an absolute requirement for Mg 2+ or Mn 2+. By the use of Ca 2+ or Zn 2+ no enzyme activity is obtained. 2. 2. In the presence of Mn 2+, in contrast to Mg 2+, always hyperbolic substrate saturation curves are obtained. 3. 3. There is evidence that Mn 2+ not only acts by forming an ADP-Mn 2+ complex, but also as an allosteric activator. 4. 4. Ca 2+ is a strong inhibitor but the enzyme becomes less sensitive to this inhibition when Mg 2+ is replaced for Mn 2.