title: Activation of alternative oxidase and uncoupling protein lowers hydrogen peroxide formation in amoeba Acanthamoeba castellanii mitochondria.
abstract: Mitochondria of amoeba Acanthamoeba castellanii were used to determine the role of two energy-dissipating systems, i.e., a free fatty acid (FFA)-activated, purine nucleotide-inhibited uncoupling protein (AcUCP) and a FFA-insensitive, purine nucleotide-activated ubiquinol alternative oxidase (AcAOX), in decreasing reactive oxygen species production in unicellular organisms. It is shown that the activation of AcUCP by externally added FFA resulted in a strong decrease in H2O2 production, whilst the inhibition of the FFA acid-induced AcUCP activity by GDP or addition of bovine serum albumin (BSA) enhanced production of H2O2. Similarly, the activation of antimycin-resistant AcAOX-mediated respiration by GMP significantly lowered H2O2 production, while inhibition of the oxidase by benzohydroxamate cancelled the GMP-induced effect on H2O2 production. When active together, both energy-dissipating systems revealed a cumulative effect on decreasing H2O2 formation. The results suggest that protection against mitochondrial oxidative stress may be a physiological role of AOX and UCP in unicellulars, such as A. castellanii.
authors.affiliation: Laboratory of Bioenergetics, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Fredry 10, 61-701 Poznan, Poland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Czarna
authors.forename: Wieslawa
authors.initials: W
authors.lastname: Jarmuszkiewicz
mesh_terms: D048248:Acanthamoeba castellanii / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007473:Ion Channels; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D024101:Mitochondrial Proteins; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011485:Protein Binding; D000071256:Uncoupling Protein 1
chemical_list: D000975:Antioxidants; D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D000071256:Uncoupling Protein 1; D006861:Hydrogen Peroxide; D010088:Oxidoreductases