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- Title
An oxo-ferryl tryptophan radical catalytic intermediate in cytochrome c and quinol oxidases trapped by microsecond freeze-hyperquenching (MHQ)
- Authors
Wiertz, Frank G.M.; Richter, Oliver-Matthias H.; Cherepanov, Alexey V.; MacMillan, Fraser; Ludwig, Bernd; de Vries, Simon
- Abstract
The pre-steady state reaction kinetics of the reduction of molecular oxygen catalyzed by fully reduced cytochrome oxidase from Escherichia coli and Paracoccus denitrificans were studied using the newly developed microsecond freeze-hyperquenching mixing-and-sampling technique. Reaction samples are prepared 60 and 200 μs after direct mixing of dioxygen with enzyme. Analysis of the reaction samples by low temperature UV–Vis spectroscopy indicates that both enzymes are trapped in the PM state. EPR spectroscopy revealed the formation of a mixture of two radicals in both enzymes. Based on its apparent <f>g</f>-value and lineshape, one of these radicals is assigned to a weakly magnetically coupled oxo-ferryl tryptophan cation radical. Implications for the catalytic mechanism of cytochrome oxidases are discussed.
- Subjects
CYTOCHROMES; HEMOPROTEINS; CYTOCHROME oxidase; ENZYMES
- Publication
FEBS Letters, 2004, Vol 575, Issue 1-3, p127
- ISSN
0014-5793
- Publication type
Article
- DOI
10.1016/j.febslet.2004.08.048