Spectroscopic description of an unusual protonated ferryl species in the catalase from Proteus mirabilis and density functional theory calculations on related models. Consequences for the ferryl protonation state in catalase, peroxidase and chloroperoxidase - BIG - Chimie et Biologie des Métaux (CBM) Accéder directement au contenu
Article Dans Une Revue JBIC Année : 2007

Spectroscopic description of an unusual protonated ferryl species in the catalase from Proteus mirabilis and density functional theory calculations on related models. Consequences for the ferryl protonation state in catalase, peroxidase and chloroperoxidase

Résumé

The catalase from Proteus mirabilis peroxide-resistant bacteria is one of the most efficient heme-containing catalases. It forms a relatively stable compound II. We were able to prepare samples of compound II from P. mirabilis catalase enriched in 57Fe and to study them by spectroscopic methods. Two different forms of compound II, namely, low-pH compound II (LpH II) and high-pH compound II (HpH II), have been characterized by Mössbauer, extended X-ray absorption fine structure (EXAFS) and UV-vis absorption spectroscopies. The proportions of the two forms are pH-dependent and the pH conversion between HpH II and LpH II is irreversible. Considering (1) the Mössbauer parameters evaluated for four related models by density functional theory methods, (2) the existence of two different Fe–Oferryl bond lengths (1.80 and 1.66 Å) compatible with our EXAFS data and (3) the pH dependence of the α band to β band intensity ratio in the absorption spectra, we attribute the LpH II compound to a protonated ferryl FeIV–OH complex (Fe–O approximately 1.80 Å), whereas the HpH II compound corresponds to the classic ferryl FeIV=O complex (Fe=O approximately 1.66 Å). The large quadrupole splitting value of LpH II (measured 2.29 mm s−1 vs. computed 2.15 mm s−1) compared with that of HpH II (measured 1.47 mm s−1 vs. computed 1.46 mm s−1) reflects the protonation of the ferryl group. The relevancy and involvement of such (FeIV=O/FeIV–OH) species in the reactivity of catalase, peroxidase and chloroperoxidase are discussed.

Dates et versions

hal-00169803 , version 1 (05-09-2007)

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Citer

Olivier Horner, Jean-Marie Mouesca, P. L. Solari, M. Orio, J.-L. Oddou, et al.. Spectroscopic description of an unusual protonated ferryl species in the catalase from Proteus mirabilis and density functional theory calculations on related models. Consequences for the ferryl protonation state in catalase, peroxidase and chloroperoxidase. JBIC, 2007, 12 (4), pp.509-525. ⟨10.1007/s00775-006-0203-9⟩. ⟨hal-00169803⟩
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