title: Effect of calcium ions on pyruvate carboxylase from pigeon liver.
abstract: Pigeon liver pyruvate carboxylase (pyruvate: CO2 ligase (ADP forming), EC 6.4.1.1) shows allosteric properties similar to those of chicken or rat liver enzyme. Kinetic methods have been used to determine the effect of Ca2+ on this enzyme. The Ca2+ activation effect is absolutely dependent on the Mg2+ concentration; in the absence of Mg2+, pyruvate carboxylase has no catalytic activity. Furthermore, Ca2+ cannot replace Mg2+ and also shows a paradoxical effect on the liver enzyme activity. It is an activator at low pyruvate or Mg2+ concentrations; at increased pyruvate concentrations, however, it becomes an inhibitor. At low levels of ATP a pronounced activation of pigeon liver pyruvate carboxylase by Ca2+ has been demonstrated. The results of this communication demonstrate pigeon liver pyruvate carboxylase to be different from pyruvate carboxylase from other sources.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D010856:Columbidae; D004305:Dose-Response Relationship, Drug; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D011766:Pyruvate Carboxylase / Q000378:metabolism*; D011773:Pyruvates / Q000378:metabolism
chemical_list: D011773:Pyruvates; D000255:Adenosine Triphosphate; D011766:Pyruvate Carboxylase; D008274:Magnesium; D002118:Calcium