Calcium-Binding Protein Isolated from Rat Liver Cytosol Reverses Activation of Pyruvate Kinase by Ca^<2+>(Biological)

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The effect of a calcium-binding protein (CaBP) isolated from rat liver cytosol on enzyme activation by Ca^<2+> was investigated. Pyruvate kinase (adenosine triphosphate: pyruvate 2-O-phosphotransferase; EC 2.7.1.40) isolated from liver cytosol was activated by addition of Ca^<2+> in the range of 1.0-10^3上3μM; the concentration giving a half-maximal effect was 10μM Ca^<2+>. The enzyme activation by 10μM Ca^<2+> addition was reversed by the presence of CaBP (4-40μg/ml). With increasing concentrations of Ca^<2+> (1,10 and 100μM Ca^<2+>), the pyruvate kinase activity increased progressively. The increase of the enzyme activity by Ca^<2+> was clearly prevented by the presence of CaBP (20μg/ml). CaBP had no effect on pyruvate kinase activity in the absence of Ca^<2+>. Meanwhile, calmodulin (2.5-10μg/ml) also reversed the activation of pyruvate kinase by Ca^<2+> (1 and 10μM). These results indicate that CaBP may regulate the activation of pyruvate kinase by Ca^<2+>. In particular,a novel CaBP may play an important role in the regulation of the Ca^<2+> effect on pyruvate kinase.
公益社団法人日本薬学会の論文
1987-05-25