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Phosphoenolpyruvate Carboxykinase Assayed at Physiological Concentrations of Metal Ions Has a High Affinity for CO2

Chen, Z., Walker, R.P., Acheson, R.M. and Leegood, R.C. (2002) Phosphoenolpyruvate Carboxykinase Assayed at Physiological Concentrations of Metal Ions Has a High Affinity for CO2. Plant Physiology, 128 (1). pp. 160-164. ISSN 0032-0889

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Abstract

The effect of Mn2+/Mg2+ concentration on the activity of intact, homogeneous phosphoenolpyruvate carboxykinase (PEPCK) from leaves of the C4 grass, Guinea grass (Panicum maximum), have been investigated. Assay conditions were optimized so that PEPCK activity could be measured at concentrations of Mn2+/Mg2+ similar to those found in the cytosol (low micromolar Mn2+ and millimolar Mg2+). PEPCK activity was totally dependent on Mn2+ and was activated at low micromolar concentrations of Mn2+ by millimolar concentrations of Mg2+. Therefore, at physiological concentrations of Mn2+, PEPCK has a requirement for Mg2+. Assay at physiological concentrations of Mn2+/Mg2+ led to a marked decrease in its affinity for ATP and a 13-fold increase in its affinity for CO2. The Km (CO2) was further decreased by assay at physiological ATP to ADP ratios, reaching values as low as 20 μM CO2, comparable with the Km (CO2) of ribulose 1,5-bisphosphate carboxylase-oxygenase. This means that PEPCK will catalyze a reversible reaction and that it could operate as a carboxylase in vivo, a feature that could be particularly important in algal CO2-concentrating systems.

Item Type: Article
Copyright, Publisher and Additional Information: © 2002 American Society of Plant Biologists
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > School of Biological Sciences (Sheffield) > Department of Animal and Plant Sciences (Sheffield)
The University of Sheffield > University of Sheffield Research Centres and Institutes > Robert Hill Institute (Sheffield)
Depositing User: Repository Officer
Date Deposited: 13 Oct 2004
Last Modified: 08 Feb 2013 16:46
Status: Published
Refereed: Yes
URI: http://eprints.whiterose.ac.uk/id/eprint/139

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