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Eukaryotic Cell, June 2007, p. 984-996, Vol. 6, No. 6
1535-9778/07/$08.00+0     doi:10.1128/EC.00061-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Carbohydrate Metabolism in the Toxoplasma gondii Apicoplast: Localization of Three Glycolytic Isoenzymes, the Single Pyruvate Dehydrogenase Complex, and a Plastid Phosphate Translocator{triangledown} ,{dagger}

Tobias Fleige,1 Karsten Fischer,2 David J. P. Ferguson,3 Uwe Gross,1 and Wolfgang Bohne1*

Institute of Medical Microbiology, University of Göttingen, Kreuzbergring 57, Göttingen D-37075, Germany,1 Institute for Biology, University of Tromsø, 9037 Tromsø, Norway,2 Nuffield Department of Pathology, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DU, England3

Received 28 February 2007/ Accepted 16 April 2007

Many apicomplexan parasites, such as Toxoplasma gondii and Plasmodium species, possess a nonphotosynthetic plastid, referred to as the apicoplast, which is essential for the parasites’ viability and displays characteristics similar to those of nongreen plastids in plants. In this study, we localized several key enzymes of the carbohydrate metabolism of T. gondii to either the apicoplast or the cytosol by engineering parasites which express epitope-tagged fusion proteins. The cytosol contains a complete set of enzymes for glycolysis, which should enable the parasite to metabolize imported glucose into pyruvate. All the glycolytic enzymes, from phosphofructokinase up to pyruvate kinase, are present in the T. gondii genome, as duplicates and isoforms of triose phosphate isomerase, phosphoglycerate kinase, and pyruvate kinase were found to localize to the apicoplast. The mRNA expression levels of all genes with glycolytic products were compared between tachyzoites and bradyzoites; however, a strict bradyzoite-specific expression pattern was observed only for enolase I. The T. gondii genome encodes a single pyruvate dehydrogenase complex, which was located in the apicoplast and absent in the mitochondrion, as shown by targeting of epitope-tagged fusion proteins and by immunolocalization of the native pyruvate dehydrogenase complex. The exchange of metabolites between the cytosol and the apicoplast is likely to be mediated by a phosphate translocator which was localized to the apicoplast. Based on these localization studies, a model is proposed that explains the supply of the apicoplast with ATP and the reduction power, as well as the exchange of metabolites between the cytosol and the apicoplast.

* Corresponding author. Mailing address: Institute of Medical Microbiology, University of Göttingen, Kreuzbergring 57, D-37075 Göttingen, Germany. Phone: 49-551-395869. Fax: 49-551-395861. E-mail: wbohne{at}gwdg.de

{triangledown} Published ahead of print on 20 April 2007.

{dagger} Supplemental material for this article may be found at http://ec.asm.org/.

Eukaryotic Cell, June 2007, p. 984-996, Vol. 6, No. 6
1535-9778/07/$08.00+0     doi:10.1128/EC.00061-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



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  • DeRocher, A. E., Coppens, I., Karnataki, A., Gilbert, L. A., Rome, M. E., Feagin, J. E., Bradley, P. J., Parsons, M. (2008). A Thioredoxin Family Protein of the Apicoplast Periphery Identifies Abundant Candidate Transport Vesicles in Toxoplasma gondii. Eukaryot Cell 7: 1518-1529 [Abstract] [Full Text]  
  • Mazumdar, J., Striepen, B. (2007). Make It or Take It: Fatty Acid Metabolism of Apicomplexan Parasites. Eukaryot Cell 6: 1727-1735 [Full Text]  


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