title: Phosphoglycerate mutase from Trypanosoma brucei is hyperactivated by cobalt in vitro, but not in vivo.
abstract: 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 Co(2+) 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 Mg(2+), Zn(2+) and Fe(2+) were the most abundant, whereas Co(2+) was below the limit of detection (<0.035 μM). The low concentration indicates that Co(2+) is unlikely to be the biologically relevant metal, but that instead, Mg(2+) and/or Zn(2+) may assume this role. Results from metal analysis of purified Leishmania mexicana iPGAM by inductively coupled plasma-mass spectrometry also show high concentrations of Mg(2+) and Zn(2+), and are consistent with this proposal. Our data suggest that in vivo cellular conditions lacking Co(2+) are unable to support the maximal activity of iPGAM, but instead maintain its activity at a relatively low level by using Mg(2+) and/or Zn(2+). The physiological significance of these observations is being pursued by structural, biochemical and biophysical studies.
authors: Institute of Structural and Molecular Biology, University of Edinburgh, Edinburgh, UK.
authors: Fazia Adyani Ahmad
authors: FA
authors: Fuad
authors: Linda A
authors: LA
authors: Fothergill-Gilmore
authors: Matthew W
authors: MW
authors: Nowicki
authors: Lorna J
authors: LJ
authors: Eades
authors: Hugh P
authors: HP
authors: Morgan
authors: Iain W
authors: IW
authors: McNae
authors: Paul A M
authors: PA
authors: Michels
authors: Malcolm D
authors: MD
authors: Walkinshaw
mesh_terms: D003035:Cobalt / Q000032:analysis / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D007501:Iron / Q000032:analysis / Q000378:metabolism; D008274:Magnesium / Q000032:analysis / Q000378:metabolism; D013058:Mass Spectrometry; D008958:Models, Molecular; D010736:Phosphoglycerate Mutase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000737:chemistry / Q000201:enzymology*; D015032:Zinc / Q000032:analysis / Q000378:metabolism
chemical_list: D003035:Cobalt; D007501:Iron; D010736:Phosphoglycerate Mutase; D008274:Magnesium; D015032:Zinc