Production of ATP by the glycolytic pathway in the mammalian pathogenic stage of protists from the genus Trypanosoma is required for the survival of the parasites. Cofactor-independent phosphoglycerate mutase (iPGAM) is particularly attractive as a drug target because it shows no similarity to the corresponding enzyme in humans, and has also been genetically validated as a target by RNAi experiments. It has previously been shown that trypanosomatid iPGAMs require Co2+ to reach maximal activity, but the biologically relevant metal has remained unclear. In this paper the metal content in the cytosol of procyclic and bloodstream-form T. brucei (analysed by inductively coupled plasma-optical emission spectroscopy) shows that Mg2+, Zn2+ and Fe2+ were the most abundant, whereas Co2+ was below the limit of detection (<0.035 μM). The low concentration indicates that Co2+ is unlikely to be the biologically relevant metal, but that instead, Mg2+ and/or Zn2+ may assume this role. Results from metal analysis of purified Leishmania mexicana iPGAM by inductively coupled plasma-mass spectrometry also show high concentrations of Mg2+ and Zn2+, and are consistent with this proposal. Our data suggest that in vivo cellular conditions lacking Co2+ are unable to support the maximal activity of iPGAM, but instead maintain its activity at a relatively low level by using Mg2+ and/or Zn2+. The physiological significance of these observations is being pursued by structural, biochemical and biophysical studies.
|Number of pages||8|
|Early online date||13 Oct 2011|
|Publication status||Published - 1 Dec 2011|
|Event||The Third International Symposium on Metallomics 2011 - Munster, Germany|
Duration: 15 Jun 2011 → 18 Jun 2011