Modifications of redox equilibria with semiquinone stabilization upon pyruvate binding to L-lactate cytochrome c oxidoreductase (flavocytochrome b2) |
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Authors: | M. Tegoni J.M. Janot M.C. Silvestrini M. Brunori F. Labeyrie |
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Affiliation: | 1. Centre de Génétique Moléculaire du C.N.R.S., Laboratoire d''Enzymologie Physicochimique, 91190 Gif-sur-Yvette, France;1. Centro di Biologia Molecolare del CNR c/o Istituti di Chimica e Chimica Biologica, Facoltà di Medicina, I Università di Roma (La Sapienza), Italia;2. Dipartimento di Biochimica, Facoltà di Medicina, II Università di Roma (Tor Vergata), Italia |
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Abstract: | Spectral redox titrations of flavin and cytochrome b2 moieties of flavocytochrome b2 were achieved in the absence and in the presence of pyruvate under equilibrium conditions at 18° C; direct measurements of spin flavosemiquinone proportions have been carried out by EPR determinations at the same temperature. Our results show that the equilibria involving flavin are largely affected by the presence of pyruvate; the semiquinone proportion markedly increases almost till unit near half-reduction of cytochrome b2; at 10 mM pyruvate, the dismutation constant, increases by a factor ≥ 10. |
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Keywords: | oxidized semiquinone reduced flavin respectively oxidized |
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