title: Pyruvate transport across the plasma membrane of the bloodstream form of Trypanosoma brucei is mediated by a facilitated diffusion carrier.
abstract: The characteristics of pyruvate transport across the plasma membrane in the bloodstream form of Trypanosoma brucei were studied using [14C]pyruvate in combination with the silicone-oil centrifugation technique. We present evidence for the existence of a facilitated diffusion carrier in the plasma membrane of T. brucei which specifically mediates the translocation of pyruvate. The uptake of pyruvate followed saturation kinetics (Km 1.96 +/- 0.28 mM; Cmax 36.61 +/- 1.15 nmol pyruvate/30 sec.mg protein), after correction of the data for a nonsaturable diffusion component. The uptake of pyruvate was competitively inhibited by a number of (oxo)monocarboxylic acids, including pyruvate analogs and metabolically related substances, but not by L-lactate. The transport exhibited the phenomenon of transacceleration, indicative for the involvement of a facilitated diffusion carrier. The carrier is highly specific for pyruvate and differs from other known monocarboxylate carriers present in the mitochondrial and/or plasma membrane of other eukaryotic cells in that it does not transport L-lactate.
authors.affiliation: International Institute of Cellular and Molecular Pathology, Research Unit for Tropical Diseases, Brussels, Belgium.
authors.forename: E A
authors.initials: EA
authors.lastname: Wiemer
authors.forename: B H
authors.initials: BH
authors.lastname: Ter Kuile
authors.forename: P A
authors.initials: PA
authors.lastname: Michels
authors.forename: F R
authors.initials: FR
authors.lastname: Opperdoes
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002250:Carbon Radioisotopes; D002264:Carboxylic Acids / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D007444:Inulin / Q000378:metabolism; D007700:Kinetics; D011773:Pyruvates / Q000378:metabolism*; D019289:Pyruvic Acid; D051381:Rats; D011919:Rats, Inbred Strains / Q000097:blood; D014346:Trypanosoma brucei brucei / Q000254:growth & development / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D002264:Carboxylic Acids; D011773:Pyruvates; D019289:Pyruvic Acid; D007444:Inulin