title: Plasmodium falciparum glutamate dehydrogenase a is dispensable and not a drug target during erythrocytic development.
abstract: BACKGROUND
  Plasmodium falciparum contains three genes encoding potential glutamate dehydrogenases. The protein encoded by gdha 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 Plasmodium and, therefore, a suitable drug target.
  
  
  METHODS
  The gene encoding the NADP(H)-dependent GDHa has been disrupted by reverse genetics in P. falciparum and the effect on the antioxidant and metabolic capacities of the resulting mutant parasites was investigated.
  
  
  RESULTS
  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 D10Δgdha 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.
  
  
  CONCLUSIONS
  First, the data support the conclusion that D10Δgdha 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 in vitro 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.
authors.affiliation: Institute of Infection, Immunity & Inflammation, Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, Sir Graeme Davies Building, University of Glasgow, 120 University Place, Glasgow G12 8TA, UK.
authors.forename: Janet
authors.initials: J
authors.lastname: Storm
authors.forename: Jan
authors.initials: J
authors.lastname: Perner
authors.forename: Isabela
authors.initials: I
authors.lastname: Aparicio
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Patzewitz
authors.forename: Kellen
authors.initials: K
authors.lastname: Olszewski
authors.forename: Manuel
authors.initials: M
authors.lastname: Llinas
authors.forename: Paul C
authors.initials: PC
authors.lastname: Engel
authors.forename: Sylke
authors.initials: S
authors.lastname: Müller
mesh_terms: D017353:Gene Deletion; D005969:Glutamate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D016877:Oxidants / Q000378:metabolism / Q000633:toxicity; D018384:Oxidative Stress; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D016877:Oxidants; D005969:Glutamate Dehydrogenase