Effect of divalent ions on pigeon kidney pyruvate carboxylase.

The apparent co-operative effect of acetyl-CoA on this enzyme from different sources has been shown by various authors [l, 3-101. Although this enzyme is known to be found in appreciable quantities only in the liver and the kidney, hardly any attempt has been made to justify the inter-relationship between the positive effecters acetyl-CoA and Mg2+ in this enzyme system. Furthermore, it is also known that Mg2+ cannot be replaced by any other metal ion in the reaction catalysed by this enzyme and that Ca2+ inhibits the enzymic activity of this enzyme [7, 111. On the other hand Ca2+ has been reported to activate other mitochondrial enzymes [ 12-141. It is therefore of value to contribute further the results of experiments showing the effect of Ca2+ and Mg2+ (divalent ions), in the presence of the allosteric effector acetyl-CoA, on pyruvate carboxylase from pigeon kidney. This communication attempts to explain the interrelationship between the allosteric effecters Mg2+ and acetyl-CoA, and the effect of Ca2+ and Mg2+ on this enzyme. The