Evidence for the extracellular reduction of alpha-lipoic acid by Leishmania donovani promastigotes: a transplasma membrane redox system.
Leishmania donovani cells, capable of reducing certain electron acceptors with redox potentials at pH 7.0 down to -290 mV, outside the plasma membrane, can reduce the oxidised form of alpha-lipoic acid. alpha-Lipoic acid has been used as natural electron acceptor probe for studying the mechanism of transplasma membrane electron transport. Transmembrane alpha-lipoic acid reduction by Leishmania was not inhibited by mitochondrial inhibitors as azide, cyanide, rotenone or antimycin A, but responded to hemin, modifiers of sulphhydryl groups and inhibitor of glycolysis. The protonophores carbonyl cyanide chlorophenylhydrazone and 2,4-dinitrophenol showed inhibition of alpha-lipoic acid reduction. This transmembrane redox system differs from that of mammalian cells in respect to its sensitivity of UV irradiation and stimulation by diphenylamine. Thus a naphthoquinone coenzyme appears to be involved in alpha-lipoic acid reduction by Leishmania cells.
Datta
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Division of Medicinal Biochemistry, Department of Pharmaceutical Technology, Jadavpur University, 700 032, Calcutta, India.
Bera
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D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000528:radiation effects; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D003574:Cytochrome c Group / Q000378:metabolism; D005033:Ethylmaleimide / Q000494:pharmacology; D005292:Ferricyanides / Q000493:pharmacokinetics; D022781:Hepatocytes / Q000378:metabolism* / Q000528:radiation effects; D006801:Humans; D066298:In Vitro Techniques; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D007893:Leishmania donovani / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D008099:Liver / Q000166:cytology; D010084:Oxidation-Reduction; D051381:Rats; D008063:Thioctic Acid / Q000378:metabolism*; D014466:Ultraviolet Rays
D003574:Cytochrome c Group; D005292:Ferricyanides; C007931:hexacyanoferrate III; D002731:4-Chloromercuribenzenesulfonate; D008063:Thioctic Acid; D007501:Iron; D005033:Ethylmaleimide