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Phosphoenolpyruvate Carboxykinase Is Involved in the Decarboxylation of Aspartate in the Bundle Sheath of Maize

Wingler, A., Walker, R.P., Chen, Z. and Leegood, R.C. (1999) Phosphoenolpyruvate Carboxykinase Is Involved in the Decarboxylation of Aspartate in the Bundle Sheath of Maize. Plant Physiology, 120 (2). pp. 539-546. ISSN 0032-0889

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Abstract

We recently showed that maize (Zea mays L.) leaves contain appreciable amounts of phosphoenolpyruvate carboxykinase (PEPCK; R.P. Walker, R.M. Acheson, L.I. Técsi, R.C. Leegood [1997] Aust J Plant Physiol 24: 459–468). In the present study, we investigated the role of PEPCK in C4 photosynthesis in maize. PEPCK activity and protein were enriched in extracts from bundle-sheath (BS) strands compared with whole-leaf extracts. Decarboxylation of [4-14C]aspartate (Asp) by BS strands was dependent on the presence of 2-oxoglutarate and Mn2+, was stimulated by ATP, was inhibited by the PEPCK-specific inhibitor 3-mercaptopicolinic acid, and was independent of illumination. The principal product of Asp metabolism was phosphoenolpyruvate, whereas pyruvate was a minor product. Decarboxylation of [4-14C]malate was stimulated severalfold by Asp and 3-phosphoglycerate, was only slightly reduced in the absence of Mn2+ or in the presence of 3-mercaptopicolinic acid, and was light dependent. Our data show that decarboxylation of Asp and malate in BS cells of maize occurs via two different pathways: Whereas malate is mainly decarboxylated by NADP-malic enzyme, decarboxylation of Asp is dependent on the activity of PEPCK.

Item Type: Article
Copyright, Publisher and Additional Information: © 1999 American Society of Plant Physiologists
Institution: The University of Sheffield
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: 12 Oct 2004
Last Modified: 05 Jun 2014 11:11
Status: Published
Refereed: Yes
URI: http://eprints.whiterose.ac.uk/id/eprint/138

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