Jarmuszkiewicz 2005 Biochim Biophys Acta: Difference between revisions

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Jarmuszkiewicz W, Czarna M, Sluse FE (2005) Substrate kinetics of the Acanthamoeba castellanii alternative oxidase and the effects of GMP. Biochim. Biophys. Acta. 1708: 71-78.

» [[Has info::PMID: 15949985]]

Jarmuszkiewicz W, Czarna M, Sluse FE (2005) Biochim. Biophys. Acta

Abstract: In Acanthamoeba castellanii mitochondria, the apparent affinity values of alternative oxidase for oxygen were much lower than those for cytochrome c oxidase. For unstimulated alternative oxidase, the K_Mox values were around 4–5 μM both in mitochondria oxidizing 1 mM external NADH or 10 mM succinate. For alternative oxidase fully stimulated by 1 mM GMP, the KK_Mox values were markedly different when compared to those in the absence of GMP and they varied when different respiratory substrates were oxidized (K_Mox was around 1.2 μM for succinate and around 11 μM for NADH). Thus, with succinate as a reducing substrate, the activation of alternative oxidase (with GMP) resulted in the oxidation of the ubiquinone pool, and a corresponding decrease in K_Mox. However, when external NADH was oxidized, the ubiquinone pool was further reduced (albeit slightly) with alternative oxidase activation, and the K_Mox increased dramatically. Thus, the apparent affinity of alternative oxidase for oxygen decreased when the ubiquinone reduction level increased either by changing the activator or the respiratory substrate availability. • Keywords: Mitochondria, Alternative oxidase, Oxygen affinity, GMP stimulation, Acanthamoeba castellanii

Labels:

Organism: Bacteria

Enzyme: TCA Cycle and Matrix Dehydrogenases, Complex II; Succinate Dehydrogenase, Complex III, Complex IV; Cytochrome c Oxidase Regulation: Respiration; OXPHOS; ETS Capacity

HRR: Oxygraph-2k, Chemicals; Media

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 |year=2005
 |journal=Biochim. Biophys. Acta
-|abstract=In ''Acanthamoeba castellanii'' mitochondria, the apparent affinity values of alternative oxidase for oxygen were much lower than those for cytochrome ''c'' oxidase. For unstimulated alternative oxidase, the ''K<sub>Mox</sub>'' values were around 4–5 μM both in mitochondria oxidizing 1 mM external NADH or 10 mM succinate. For alternative oxidase fully stimulated by 1 mM GMP, the ''KK<sub>Mox</sub>'' values were markedly different when compared to those in the absence of GMP and they varied when different respiratory substrates were oxidized (''K<sub>Mox</sub>'' was around 1.2 μM for succinate and around 11 μM for NADH). Thus, with succinate as a reducing substrate, the activation of alternative oxidase (with GMP) resulted in the oxidation of the ubiquinone pool, and a corresponding decrease in ''K<sub>Mox</sub>''. However, when external NADH was oxidized, the ubiquinone pool was further reduced (albeit slightly) with alternative oxidase activation, and the ''K<sub>Mox</sub''> increased dramatically. Thus, the apparent affinity of alternative oxidase for oxygen decreased when the ubiquinone reduction level increased either by changing the activator or the respiratory substrate availability.
+|abstract=In ''Acanthamoeba castellanii'' mitochondria, the apparent affinity values of alternative oxidase for oxygen were much lower than those for cytochrome ''c'' oxidase. For unstimulated alternative oxidase, the ''K<sub>Mox</sub>'' values were around 4–5 μM both in mitochondria oxidizing 1 mM external NADH or 10 mM succinate. For alternative oxidase fully stimulated by 1 mM GMP, the ''KK<sub>Mox</sub>'' values were markedly different when compared to those in the absence of GMP and they varied when different respiratory substrates were oxidized (''K<sub>Mox</sub>'' was around 1.2 μM for succinate and around 11 μM for NADH). Thus, with succinate as a reducing substrate, the activation of alternative oxidase (with GMP) resulted in the oxidation of the ubiquinone pool, and a corresponding decrease in ''K<sub>Mox</sub>''. However, when external NADH was oxidized, the ubiquinone pool was further reduced (albeit slightly) with alternative oxidase activation, and the ''K<sub>Mox</sub>'' increased dramatically. Thus, the apparent affinity of alternative oxidase for oxygen decreased when the ubiquinone reduction level increased either by changing the activator or the respiratory substrate availability.
 |keywords=Mitochondria, Alternative oxidase, Oxygen affinity, GMP stimulation, ''Acanthamoeba castellanii''
 |info=[http://www.ncbi.nlm.nih.gov/pubmed/15949985 PMID: 15949985]