title: Enzymes of energy metabolism in the bradyzoites and tachyzoites of Toxoplasma gondii.
abstract: The bradyzoite and tachyzoite forms of Toxoplasma gondii, purified from infected animals, were analysed for their activities of phosphofructokinase, pyruvate kinase, lactate dehydrogenase, NAD(+)- and NADH-linked isocitrate dehydrogenases, and succinic dehydrogenase. Both developmental stages contained high activities of phosphofructokinase (specific for pyrophosphate rather than ATP), pyruvate kinase and lactate dehydrogenase, suggesting that energy metabolism in both forms may centre around a high glycolytic flux linked to lactate production. The markedly higher activity of the latter two enzymes in bradyzoites suggests that lactate production is particularly important in this developmental form. NAD(+)-specific isocitrate dehydrogenase was not detectable in either stage of the parasite (and proved useful as a measure of the purity of the bradyzoite preparation), whereas both parasite forms contained low activities of NADP(+)-linked isocitrate dehydrogenase. The results are consistent with the bradyzoites lacking a functional TCA cycle and respiratory chain and are suggestive of a lack of susceptibility of this developmental stage to atovaquone.
authors.affiliation: Institute of Biomedical and Life Sciences, University of Glasgow, UK.
authors.forename: H
authors.initials: H
authors.lastname: Denton
authors.forename: C W
authors.initials: CW
authors.lastname: Roberts
authors.forename: J
authors.initials: J
authors.lastname: Alexander
authors.forename: K W
authors.initials: KW
authors.lastname: Thong
authors.forename: G H
authors.initials: GH
authors.lastname: Coombs
mesh_terms: D000818:Animals; D002952:Citric Acid Cycle; D004734:Energy Metabolism; D006019:Glycolysis; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D010732:Phosphofructokinase-1 / Q000378:metabolism; D011770:Pyruvate Kinase / Q000378:metabolism; D016205:Sigmodontinae; D013385:Succinate Dehydrogenase / Q000378:metabolism; D014122:Toxoplasma / Q000201:enzymology* / Q000254:growth & development* / Q000472:pathogenicity
chemical_list: D007770:L-Lactate Dehydrogenase; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+); D013385:Succinate Dehydrogenase; D010732:Phosphofructokinase-1; D011770:Pyruvate Kinase