Regulation and roles of phosphoenolpyruvate carboxykinase in plants.
Phosphoenolpyruvate carboxykinase (PCK) is probably ubiquitous in flowering plants, but is confined to certain cells or tissues. It is regulated by phosphorylation, which renders it less active by altering both its substrate affinities and its sensitivity to regulation by adenylates. In the leaves of some C4 plants, such as Panicum maximum, dephosphorylation increases its activity in the light. In other tissues such regulation probably avoids futile cycling between phosphoenolpyruvate and oxaloacetate. Although PCK generally acts as a decarboxylase in plants, its affinity for CO2 measured at physiological concentrations of metal ions is high and would allow it to be freely reversible in vivo. While its function in gluconeogenesis in seeds postgermination and in leaves of C4 and crassulacean acid metabolism plants is clearly established, the possible functions of PCK in other plant cells are discussed, drawing parallels with those in animals, including its integrated function in cataplerosis, nitrogen metabolism, pH regulation, and gluconeogenesis.
Leegood
Richard C
RC
Robert Hill Institute and Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK. r.leegood@sheffield.ac.uk <r.leegood@sheffield.ac.uk>
Walker
Robert P
RP
D000255:Adenosine Triphosphate / Q000378:metabolism; D029627:Crassulaceae / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism; D010071:Oxaloacetates / Q000494:pharmacology; D010766:Phosphorylation; D010944:Plants / Q000201:enzymology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism* / Q000502:physiology*; D013997:Time Factors
D010071:Oxaloacetates; D000255:Adenosine Triphosphate; C069767:phosphoenolpyruvate carboxylase kinase; D017346:Protein Serine-Threonine Kinases; D005947:Glucose; D009584:Nitrogen