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Plant Physiology 54:617-623 (1974)
© 1974 American Society of Plant Biologists

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Articles

Some Properties of Partially Purified Pyruvate Kinase from Euglena gracilis Klebs var. bacillaris1

Dennis Vaccaro2 and Michael H. Zeldin3

a Department of Biology, Tufts University, Medford, Massachusetts 02155

A method of purification of pyruvate kinase (EC 2.7.1.40) from light-grown Euglena gracilis var. bacillaris was developed which yielded an enzyme preparation purified 115-fold over crude extracts. During organelle formation, levels of pyruvate kinase in extracts prepared from cells engaged in light-induced chloroplast development do not change significantly. The enzyme has a molecular weight of approximately 240,000 and a requirement for both K+ and Mg2+. Fructose 1,6-diphosphate activates the enzyme when the concentration of phosphoenol-pyruvate is limiting; it does not activate when the concentration of ADP is limiting. ATP, citrate, and Ca2+ are inhibitors of the enzyme and inhibit the fructose 1,6-diphosphate stimulation of the enzyme activity. ATP inhibition is only partially reversed by high concentrations of fructose 1,6-diphosphate. Further reversal of inhibition can be achieved by dialysis. Ca2+-dependent inhibition can be reversed by a chelating agent but not by increased concentrations of Mg2+.

The significance of the properties of pyruvate kinase in the regulation of photosynthetic carbohydrate metabolism, especially in connection with the inability of fructose 1,6-diphosphate to reverse Ca2+ and ATP inhibitions, is emphasized.

2 Present address: Department of Physiology, Harvard Medical School, Boston, Mass.

3 Present address: Biological Laboratories, Harvard University, Cambridge, Mass.

1 This work was supported in part by National Science Foundation Grant GB-27502 and by Tufts University Faculty Research Fund.






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