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Le Quoc K, Le Quoc D, Gaudemer Y: Influence of the energetic state of mitochondria on the inhibition of oxidative phosphorylation by N-ethylmaleimide. Biochim Biophys Acta. 1979 May 9;546(2):356-64.
N-Ethylmaleimide inhibitory effect on oxidative phosphorylation, adenylic nucleotide translocation, succinate dehydrogenase and succinoxidase activities was studied as a function of the energetic state of mitochondria. 1. Using a reversible thiol reagent (mersalyl), in order to protect the phosphate carrier against irreversible action of N-ethylmaleimide, it was found that: (a) when mersalyl-pretreated mitochondria were in a 'non-energized' state, i.e. preincubated without a substrate and in the presence of rotenone, only a slight inhibition of succinate oxidation coupled to ATP synthesis by N-ethylmaleimide was observed. (b) when mersalyl-pretreated mitochondria were in an 'energized' state, i.e. preincubated in the presence of an oxidizable substrate, N-ethylmaleimide strongly inhibited the coupled oxidation of succinate. 2. Mitochondrial energization was also shown to enhavce the inhibitory effect of N-ethylmaleimide on adenylic nucleotide translocation and succinoxidase activity. However, other sulphydrul groups seem to be involved in the inhibition mechanism, but their function is unknown. 3. As N-ethylmaleimide inhibitory effect increased, an enhancement of N-[14C] ethylmaleimide binding to mitochondrial sulphydryl groups was obtained. |
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