ELECTRON SPIN RESONANCE ABSORPTIONS OF CYTOCHROME c PEROXIDASE AND COMPLEX ES IN DISSOLVED AND CRYSTALLINE STATES

Yonetani, Takashi; Schleyer, Heinz; Ehrenberg, Anders

doi:10.1016/b978-1-4832-1333-0.50022-7

Cited by 31 publications

(63 citation statements)

References 13 publications

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“…The positive correlation between the ability of horseradish peroxidase to activate Hz02 and the need to bind H+ with F-[ 171 provides evidence for a common denominator in all these abnormalities. Extrapolation of curve b in fig.2 gives a value of log k = 8.4 for reaction of MP-8 with the fully formed HO; (assuming pK 11.7 [ 14]), which is close to the value of log k = 8.1 reported [18] for the reaction of cytochrome c peroxidase with H202; this provides evidence for a common denominator in the reactions of MP-8 and peroxidase after allowance is made for the abnormal proton uptake by the peroxidases. The primary role of the protein is, therefore, to convert the simple reaction with HO;, as observed with MP-8, into a proton-coupled reaction; this enables the enzyme to bind Hz02 as H+ and the required HOT in a pH-independent equilibrium [3].…”

Section: Discussionmentioning

confidence: 60%

Mechanism of activation of H₂O₂ by peroxidases: kinetic studies on a model system

1985

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Kinetic studies on the peroxidase activity of microperoxidase-8 at pH 5. 5-8.5 show that the rate is increased by raising the pH or by the presence of guanidinium ion. Comparison with published data on the peroxidases provides evidence that the enzyme activates H202 through the cooperative binding of H+ + HO; and suggests a role for the invariant distal Arg.Peroxidase Proton-coupled reaction Arginine

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Section: Discussionmentioning

confidence: 60%

Mechanism of activation of H₂O₂ by peroxidases: kinetic studies on a model system

1985

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“…IV ϭO Por), equivalent to compound II of peroxidase, paired with a protein radical as reported previously (22)(23)(24). The ferryl heme (Mb-II) formation in wild-type Mb showed isosbestic points and obeyed pseudo first-order kinetics.…”

Section: Reactions Of Ferric Myoglobins With H 2 O 2 -Ferric Wild-typmentioning

confidence: 95%

“…Whereas the distal histidine in peroxidase is suggested to raise the basicity of imidazole by a hydrogen bond with the adjacent asparagine (20,21), the absence of the hydrogen bond in Mb (13,14) is indicative of less basicity of its distal histidine. Furthermore, wild-type Mb cleaves the O-O bond of the heme-bound peroxide not only heterolytically, but also homolytically to give Mb-II and a hydroxy radical as shown in Scheme II (22)(23)(24). It has been suggested that the distal histidine in Mb is unable to enhance heterolysis as a general acid (25); however, the structural factor for this inability is still obscure.…”

mentioning

confidence: 99%

Effects of the Location of Distal Histidine in the Reaction of Myoglobin with Hydrogen Peroxide

Matsui¹,

Ozaki²,

Liong³

et al. 1999

Journal of Biological Chemistry

185

249

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To clarify how the location of distal histidine affects the activation process of H 2 O 2 by heme proteins, we have characterized reactions with H 2 O 2 for the L29H/ H64L and F43H/H64L mutants of sperm whale myoglobin (Mb), designed to locate the histidine farther from the heme iron. Whereas the L29H/H64L double substitution retarded the reaction with H 2 O 2 , an 11-fold rate increase versus wild-type Mb was observed for the F43H/ H64L mutant. The V max values for 1-electron oxidations by the myoglobins correlate well with the varied reactivities with H 2 O 2 . The functions of the distal histidine as a general acid-base catalyst were examined based on the reactions with cumene hydroperoxide and cyanide, and only the histidine in F43H/H64L Mb was suggested to facilitate heterolysis of the peroxide bond. The x-ray crystal structures of the mutants confirmed that the distal histidines in F43H/H64L Mb and peroxidase are similar in distance from the heme iron, whereas the distal histidine in L29H/H64L Mb is located too far to enhance heterolysis. Our results indicate that the proper positioning of the distal histidine is essential for the activation of H 2 O 2 by heme enzymes.Peroxidase is a heme enzyme that catalyzes 1-electron oxidations of a variety of substrates (1, 2). The ferric enzyme is oxidized by H 2 O 2 to yield a ferryl porphyrin cation radical (Fe IV ϭO Por . ϩ ) known as compound I in the first step of the catalytic cycle (3). Compound I is reduced to the ferric state through a ferryl species (Fe IV ϭO Por), so-called compound II, by two sequential 1-electron oxidations of substrates. The invariant histidine in the distal heme pocket (1-6) is a critical residue for peroxidases, and its replacement by aliphatic residues retards compound I formation by 5ϳ6 orders of magnitude (7-9). As shown in Scheme I, the distal histidine is believed to function (i) as a general base to accelerate binding of H 2 O 2 to the ferric heme iron by deprotonating the peroxide and (ii) as a general acid to facilitate the heterolytic cleavage of the O-O bond of a plausible Fe III ⅐OOH complex by protonating the terminal oxygen atom (10). The charge separation in heterolysis is suggested to be also enhanced by a positively charged distal arginine (Scheme I), whose substitution results in 2 orders of magnitude slower formation of compound I (10 -12).Myoglobin (Mb), 1 a carrier of molecular oxygen, similarly possesses a distal histidine (His-64) in the heme pocket ( Fig. 1 might be partly due to the malfunction of the distal histidine as a general acid-base catalyst and the absence of the distal arginine. Whereas the distal histidine in peroxidase is suggested to raise the basicity of imidazole by a hydrogen bond with the adjacent asparagine (20, 21), the absence of the hydrogen bond in Mb (13, 14) is indicative of less basicity of its distal histidine. Furthermore, wild-type Mb cleaves the O-O bond of the heme-bound peroxide not only heterolytically, but also homolytically to give Mb-II and a hydroxy radical as shown in Scheme...

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“…ES is at the same level of oxidation as compound I of horseradish peroxidase and of catalase (5) but is quite unlike them in several respects. It is remarkably stable (4); optical spectra (2), M6ss-bauer spectra (6), and static susceptibility measurements (7) indicate that it contains an S = 1, Fe(IV) heme and a species with S = 1/2; it exhibits an intense electron paramagnetic resonance (EPR) signal (8,9).…”

mentioning

confidence: 99%

Electron-nuclear double resonance of the hydrogen peroxide compound of cytochrome c peroxidase: identification of the free radical site with a methionyl cluster.

Hoffman¹,

Roberts²,

Brown³

et al. 1979

Proc. Natl. Acad. Sci. U.S.A.

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The results of electron-nuclear double resonance and electron paramagnetic resonance (EPR) studies on the hydrogen peroxide compound of yeast cytochrome c peroxidase are inconsistent with previous proposals for the source of the EPR signal in this compound, in particular with its identification with an aromatic amino acid radical such as would arise by oxidation of a tryptophanyl side chain. The present observations lead us to propose that the EPR signal is associated with a cluster containing at least one methionine and in which proximate side chains share the charge created by loss of one electron.

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ELECTRON SPIN RESONANCE ABSORPTIONS OF CYTOCHROME c PEROXIDASE AND COMPLEX ES IN DISSOLVED AND CRYSTALLINE STATES

Cited by 31 publications

References 13 publications

Mechanism of activation of H₂O₂ by peroxidases: kinetic studies on a model system

Mechanism of activation of H₂O₂ by peroxidases: kinetic studies on a model system

Effects of the Location of Distal Histidine in the Reaction of Myoglobin with Hydrogen Peroxide

Electron-nuclear double resonance of the hydrogen peroxide compound of cytochrome c peroxidase: identification of the free radical site with a methionyl cluster.

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ELECTRON SPIN RESONANCE ABSORPTIONS OF CYTOCHROME c PEROXIDASE AND COMPLEX ES IN DISSOLVED AND CRYSTALLINE STATES

Cited by 31 publications

References 13 publications

Mechanism of activation of H2O2 by peroxidases: kinetic studies on a model system

Mechanism of activation of H2O2 by peroxidases: kinetic studies on a model system

Effects of the Location of Distal Histidine in the Reaction of Myoglobin with Hydrogen Peroxide

Electron-nuclear double resonance of the hydrogen peroxide compound of cytochrome c peroxidase: identification of the free radical site with a methionyl cluster.

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Mechanism of activation of H₂O₂ by peroxidases: kinetic studies on a model system

Mechanism of activation of H₂O₂ by peroxidases: kinetic studies on a model system