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Enzymatic Regulation of the Metabolism of Phosphoenolpyruvate in Tetrahymena pyriformis

1972; Elsevier BV; Volume: 247; Issue: 9 Linguagem: Inglês

10.1016/s0021-9258(19)45276-9

1083-351X

Martin Diesterhaft, Hsiang-Chuan Hsieh, Charles E. Elson, H.J. Sallach, Earl Shrago,

Amino Acid Enzymes and Metabolism

Abstract The enzymes of phosphoenolpyruvate metabolism, i.e. P-enolpyruvate carboxykinase, P-enolpyruvate carboxylase, and pyruvate kinase, have been compared in Tetrahymena pyriformis under growth conditions which favor either gluconeogenesis or glycolysis. The activity of the cytosol P-enolpyruvate carboxykinase is high in glucose-free and low in glucose-supplemented medium, while there is no change in activity of the mitochondrial enzyme. The chromatographic separation of the cytosol and mitochondrial enzymes on DEAE-Sephadex and Sephadex G-200 indicate that they are isozymes with distinct molecular properties. Both P-enolpyruvate carboxylase and pyruvate kinase activities are higher in glucose-supplemented medium. Distribution studies indicate an exclusive mitochondrial location for P-enolpyruvate carboxylase and cytosol location for pyruvate kinase. The peroxisomal enzymes, isocitrate lyase, malate synthetase, and lactic acid oxidase, as well as the cytosol P-enolpyruvate carboxykinase, adapt to changes in aeration as well as to glucose supplementation of the culture. Certain important enzymatic similarities as well as differences were observed between Tetrahymena and other organisms, including mammals.