Electron paramagnetic and electron nuclear double resonance of the hydrogen peroxide compound of cytochrome c peroxidase. Academic Article uri icon


  • We have collected electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectra from the hydrogen peroxide compound of yeast cytochrome c peroxidase, termed ES, employing EPR microwave frequencies of 9.6 and 11.6 GHz. We have measured and analyzed the temperature dependence of the spin-lattice relaxation rate (1/T1) of the paramagnetic center of ES over the temperature range 1.9 to 4 K. In addition, an upper bound to exchange coupling between the ferryl heme and EPR-visible centers of ES has been calculated and expressions for the dipolar interaction between a ferryl heme and a free radical have been derived. These results all confirm that the EPR signal of ES is not associated with an aromatic amino acid radical, and in particular not with a tryptophanyl radical. This conclusion has led us to consider an explanation of the EPR signal in terms of a nucleophilically stabilized methionyl radical.

published proceedings

  • J Biol Chem

author list (cited authors)

  • Hoffman, B. M., Roberts, J. E., Kang, C. H., & Margoliash, E

citation count

  • 106

complete list of authors

  • Hoffman, BM||Roberts, JE||Kang, CH||Margoliash, E

publication date

  • July 1981