PEP carboxylase kinase is a novel protein kinase controlled at the level of expression

Authors

  • Hugh G. Nimmo,

    Corresponding author
    1. Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
    Search for more papers by this author
  • Véronique Fontaine,

    1. Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
    Search for more papers by this author
  • James Hartwell,

    1. Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
    Search for more papers by this author
  • Gareth I. Jenkins,

    1. Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
    Search for more papers by this author
  • Gillian A. Nimmo,

    1. Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
    Search for more papers by this author
  • Malcolm B. Wilkins

    1. Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
    Search for more papers by this author

Summary

Phosphoenolpyruvate (PEP) carboxylase plays a number of key roles in the central metabolism of higher plants. The enzyme is regulated by reversible phosphorylation in response to a range of signals in many different plant tissues. The data discussed here illustrate several novel features of this system. The phosphorylation state of PEP carboxylase is controlled largely by the activity of PEP carboxylase kinase. This enzyme comprises a protein kinase catalytic domain with no regulatory regions. In many systems it is controlled at the level of expression. In C4 plants, expression of PEP carboxylase kinase is light-regulated and involves changes in cytosolic pH, InsP3 and Ca2+ levels. Expression of PEP carboxylase kinase in CAM plants is regulated by a circadian oscillator, perhaps via metabolite control. Some plants contain multiple PEP carboxylase kinase genes, probably with different expression patterns and roles. A newly discovered PEP carboxylase kinase inhibitor protein might facilitate the net dephosphorylation of PEP carboxylase under conditions in which flux through this enzyme is not required.

Ancillary