<it>Plasmodium falciparum </it>glutamate dehydrogenase a is dispensable and not a drug target during erythrocytic development

• Main Authors: Engel Paul C, Llinas Manuel, Olszewski Kellen, Patzewitz Eva-Maria, Aparicio Isabela, Perner Jan, Storm Janet, Müller Sylke
• Format: Article
• Language: English
• Published: BMC 2011-07-01
• Series: Malaria Journal
• Online Access: http://www.malariajournal.com/content/10/1/193

<p>Abstract</p> <p>Background</p> <p><it>Plasmodium falciparum </it>contains three genes encoding potential glutamate dehydrogenases. The protein encoded by <it>gdha </it>has previously been biochemically and structurally characterized. It was suggested that it is important for the supply of reducing equivalents during intra-erythrocytic development of <it>Plasmodium </it>and, therefore, a suitable drug target.</p> <p>Methods</p> <p>The gene encoding the NADP(H)-dependent GDHa has been disrupted by reverse genetics in <it>P. falciparum </it>and the effect on the antioxidant and metabolic capacities of the resulting mutant parasites was investigated.</p> <p>Results</p> <p>No growth defect under low and elevated oxygen tension, no up- or down-regulation of a number of antioxidant and NADP(H)-generating proteins or mRNAs and no increased levels of GSH were detected in the D10^{Δ<it>gdha </it>}parasite lines. Further, the fate of the carbon skeleton of [¹³C] labelled glutamine was assessed by metabolomic studies, revealing no differences in the labelling of α-ketoglutarate and other TCA pathway intermediates between wild type and mutant parasites.</p> <p>Conclusions</p> <p>First, the data support the conclusion that D10^{Δ<it>gdha </it>}parasites are not experiencing enhanced oxidative stress and that GDHa function may not be the provision of NADP(H) for reductive reactions. Second, the results imply that the cytosolic, NADP(H)-dependent GDHa protein is not involved in the oxidative deamination of glutamate but that the protein may play a role in ammonia assimilation as has been described for other NADP(H)-dependent GDH from plants and fungi. The lack of an obvious phenotype in the absence of GDHa may point to a regulatory role of the protein providing glutamate (as nitrogen storage molecule) in situations where the parasites experience a limiting supply of carbon sources and, therefore, under <it>in vitro </it>conditions the enzyme is unlikely to be of significant importance. The data imply that the protein is not a suitable target for future drug development against intra-erythrocytic parasite development.</p>