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Biochem J. May 1969; 112(5): 549–558.
PMCID: PMC1187755

Studies on the mechanism of activation and inactivation of pyruvate,phosphate dikinase. A possible regulatory role for the enzyme in the C4 dicarboxylic acid pathway of photosynthesis


1. The activity of pyruvate,Pi dikinase in leaves of maize and Amaranthus palmeri rapidly falls on transferring illuminated plants to darkness. Illumination of dark-treated plants results in an immediate rapid increase in activity of the enzyme, the final activity reached being dependent on the intensity of the incident light. 2. Activation of the enzyme in extracts of dark-treated maize leaves after gel filtration on Sephadex G-25 requires a thiol and Pi. The Pi requirement for activation can be replaced by arsenate. Activation of the enzyme is inhibited by AMP and GMP and possibly also by ADP and ATP. Activation of the enzyme after gel filtration on Sephadex G-200 also requires a heat-labile component that is excluded by Sephadex G-25. 3. The active enzyme isolated from illuminated leaves is inactivated by ADP in the presence of a thiol, the rate of inactivation being very much faster in air than in an oxygen-free atmosphere. Reactivation of the ADP-inactivated enzyme requires a thiol, Pi and a component excluded by Sephadex G-25 but considerably retarded by Sephadex G-200. 4. The active enzyme is rapidly and irreversibly inactivated in the absence of a thiol. Inactivation is accelerated by both sodium diethyldithiocarbamate and tetraethylthiuram disulphide, and the enzyme inactivated by these reagents is completely reactivated by incubation with dithiothreitol. This reactivation does not require Pi. The inactive enzyme from dark-treated leaves is stabilized by diethyldithiocarbamate and can be partially activated by dithiothreitol alone; complete reactivation requires both dithiothreitol and Pi. 5. The enzyme activity is markedly inhibited by the thiol reagents p-chloromercuribenzoate, γ-(p-arsenophenyl)-n-butyrate and an equimolar mixture of arsenite and 2,3-dimercaptopropan-1-ol. 6. The processes of activation and inactivation observed in vitro are discussed in relation to the regulation of pyruvate,Pi dikinase activity in the leaf.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Cooper RA, Kornberg HL. The direct synthesis of phosphoenolpyruvate from pyruvate by Escherichia coli. Proc R Soc Lond B Biol Sci. 1967 Sep 12;168(1012):263–280. [PubMed]
  • Hatch MD, Slack CR. Photosynthesis by sugar-cane leaves. A new carboxylation reaction and the pathway of sugar formation. Biochem J. 1966 Oct;101(1):103–111. [PMC free article] [PubMed]
  • Hatch MD, Slack CR. A new enzyme for the interconversion of pyruvate and phosphopyruvate and its role in the C4 dicarboxylic acid pathway of photosynthesis. Biochem J. 1968 Jan;106(1):141–146. [PMC free article] [PubMed]
  • Hatch MD, Slack CR, Johnson HS. Further studies on a new pathway of photosynthetic carbon dioxide fixation in sugar-cane and its occurrence in other plant species. Biochem J. 1967 Feb;102(2):417–422. [PMC free article] [PubMed]
  • Reeves RE. A new enzyme with the glycolytic function of pyruvate kinase. J Biol Chem. 1968 Jun 10;243(11):3202–3204. [PubMed]
  • Slack CR, Hatch MD. Comparative studies on the activity of carboxylases and other enzymes in relation to the new pathway of photosynthetic carbon dioxide fixation in tropical grasses. Biochem J. 1967 Jun;103(3):660–665. [PMC free article] [PubMed]

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