Electron Spin Resonance Investigation of the Cyanyl and Azidyl Radical Formation by Cytochrome c Oxidase
Year: 1999
Type: article
Abstract: Cyanide (CN(-)) is a frequently used inhibitor of mitochondrial respiration due to its binding to the ferric heme a(3) of cytochrome c oxidase (CcO). As-isolated CcO oxidized cyanide to the cyanyl radical ((.)CN) that was detected, using the ESR spin-trapping technique, as the 5,5-dimethyl-1-pyrroline N-oxide (DMPO)/(.)CN radical adduct. The enzymatic conversion of cyanide to the cyanyl radical by CcO was time-dependent but not affected by azide (N(3)(-)). The small but variable amounts of compound P present in the as-isolated CcO accounted for this one-electron oxidation of cyanide to the cyanyl radical. In contrast, as-isolated CcO exhibited little ability to catalyze the oxidation of azide, presumably because of azide's lower affinity for the CcO. However, the DMPO/(.)N(3) radical adduct was readily detected when H(2)O(2) was included in the system. The results presented here indicate the need to re-evaluate oxidative stress in mitochondria "chemical hypoxia" induced by cyanide or azide to account for the presence of highly reactive free radicals.
Source: Journal of Biological Chemistry
Language: English
Subfield: Inorganic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1987684507