[Effect of Ca2+ ions on the pyruvate kinase isoenzymes from rabbit kidney cortex]

Ca2 ions showed the various effect on isoenzymes of pyruvate kinase from rabbit kidney cortex. Ca2 activated the "L" type of pyruvate kinase at low concentrations of PEP and inhibited -- at high concentrations of the latter. "M2" type of pyruvate kinase was inhibited by Ca2 under all the conditions studied. In presence of Ca2+ the activating effect of PDP on "L" and "M2" types of pyruvate kinase was absent; the inhibitory action of ATP on the "M" type of pyruvate kinase was increased at all the concentrations above 1.3 mM. The effect of Ca2+ on the pyruvate kinase isoenzymes depended on content of Mg2+ in the medium.