title: Characterization of mitochondrial electron-transfer in Leishmania mexicana.
abstract: Some general features of the respiratory chain and respiratory control were characterized in coupled mitochondrial preparations from Leishmania mexicana promastigotes. O2 uptake was sensitive to the electron-transfer inhibitors rotenone, flavone, malonate, 4,4,4-trifluoro-1-(2-thienyl) 1.3 butanedione (TTFA), antimycin A, 2n-nonyl-4-hydroxyquinoline-N-oxide (HQNO), myxothiazol, cyanide and azide. A high concentration of rotenone (60 microM) was required to inhibit O2 uptake effectively. Difference spectra revealed the presence of cytochromes (a + a3), b and c. Respiratory control was stimulated 2-fold by ADP with different exogenous oxidizable substrates. Calculated ADP/O ratios were consistent with the notion that ascorbate/N,N,N',N'-tetramethylphenylenediamine (TMPD)-linked and FAD-linked respiration proceeds, respectively, with one third and two thirds of the ATP producing capacity of NADH-linked respiration. State 3 was suppressed by the ATP synthase inhibitors oligomycin and aurovertin and by the adenine nucleotide translocator inhibitors atractyloside and carboxy atractyloside. The protonophore carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP) provoked state 3u respiration. The mitochondrial preparation was capable of Ca2+ uptake and Ca2+ stimulated respiration. Data obtained suggests strongly that mitochondrial complexes I, II, III and IV are present in a major pathway of electron-transfer and that oxidative phosphorylation might proceed with high bioenergetic efficiency.
authors.affiliation: Instituto de Biología Experimental, Facultad de Ciencias, Universidad Central de Venezuela, Caracas.
authors.forename: R
authors.initials: R
authors.lastname: Bermúdez
authors.forename: F
authors.initials: F
authors.lastname: Dagger
authors.forename: J A
authors.initials: JA
authors.lastname: D'Aquino
authors.forename: G
authors.initials: G
authors.lastname: Benaim
authors.forename: K
authors.initials: K
authors.lastname: Dawidowicz
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002458:Cell Fractionation; D019069:Cell Respiration; D003580:Cytochromes / Q000378:metabolism; D004579:Electron Transport / Q000187:drug effects; D007425:Intracellular Membranes / Q000201:enzymology / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D007894:Leishmania mexicana / Q000201:enzymology / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption / Q000187:drug effects; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D013057:Spectrum Analysis
chemical_list: D003580:Cytochromes; D009243:NAD; D000244:Adenosine Diphosphate; D000226:Mitochondrial ADP, ATP Translocases; D006180:Proton-Translocating ATPases; D002118:Calcium