Cytochrome c peroxidase and

EXAFS data indicated an Fe=0 bond length of 1.65 0.05 A, similar to that found for compound I intermediates in several enzymes such as catalases, horseradish peroxidase, cytochrome c peroxidase, and chloroperoxidases. 

Cyclic voltammetry has been also used for estimation of the rate constants for oxidation of water-soluble ferrocenes in the presence of HRP (131). There is a perfect match between the data obtained spectrophotometrically and electrochemically (Table IV), which proves that the cyclic voltammetry reveals information on the oxidation of ferrocenes by Compound II. It is interesting to note that an enzyme similar to HRP, viz. cytochrome c peroxidase, which catalyzes the reduction of H202 to water using two equivalents of ferrocytochrome c (133-136), is ca. 100 times more reactive than HRP (131,137). The second-order rate constant equals 1.4 x 106 M-1 s 1 for HOOCFc at pH 6.5 (131). There is no such rate difference in oxidation of [Fe(CN)e]4- by cytochrome c peroxidase and HRP (8). These comparisons should not however create an impression that the enzymatic oxidation of ferrocenes is always fast. The active-R2 subunit of Escherichia coli ribonucleotide reductase, which has dinuclear nonheme iron center in the active site, oxidizes ferrocene carboxylic acid and other water-soluble ferrocenes with a rate constant of... 

Long range electron-transfer has also been demonstrated within the complex between zinc-substituted cytochrome c peroxidase and cyt c 59). The kinetics of intramolecular electron-transfer from Ru(II) to Fe(III) in ruthenium modified cyt c has also been investigated 58). 

Crystal-structure of a complex between electron-transfer partners, cytochrome-c peroxidase and cytochrome c, Pelletier, H. Kraut, J. Science 1992, 258,1748-1755. 

Most peroxidases are glycoproteins (exceptions are cytochrome c peroxidase and myeloperoxidase). The purpose of the carbohydrate component in these enzymes is uncertain. However, horseradish peroxidase has long been known to be a very stable enzyme, even under conditions of high temperature. In part this may be due to the carbohydrate component. Table 5-2 summarises some of the properties of the peroxidases and the spectral parameters are summarised in Table 5-3. 

Geren L, Hahm S, Durham B, Millett F. Photoinduced electron transfer between cytochrome c peroxidase and yeast cytochrome c labeled at Cys 102 with (4-bromomethyl-4 -methylbipyridine)[bis(bipyridine)]ruthenium2+. Biochemistry 1991 30 9450-7. 

Ascorbate Peroxidases, Cytochrome c Peroxidases, and Their Putative Hybrid Types... 

Conroy CW, Tyma P, Daum PH et al (1978) Oxidation-reduction potential measurements of cytochrome c peroxidase and pH dependent spectral transitions in the ferrous enzyme. Biochim Biophys Acta 537 62-69... 

Jensen GM, Bunte SW, Warshel A et al (1998) Energetics of cation radical formation at the proximal active site tryptophan of cytochrome c peroxidase and ascorbate peroxidase. J Phys Chem B 102 8221-8228... 

Vitello LB, Erman JE, Miller MA et al (1993) Effect of arginine-48 replacement on the reaction between cytochrome c peroxidase and hydrogen peroxide. Biochemistry 32 9807-9818... 

The elucidation of the mode of interaction between cytochrome c peroxidase and cytochrome c is not only essential in our understanding of the reaction mechanism of this enzyme but also provides important clues for formulating a general mechanism of electron transfer in biological sys-... 

The formation of a reversible Michaelis-Menten-type complex of the enzyme and ferrocytochrome c [ES1S2 in Eq. (3) ] can be postulated from initial steady-state kinetics of the cytochrome c peroxidase reaction (17). Since cytochrome c peroxidase and cytochrome c are acidic and basic proteins, respectively, their interaction may be governed principally by electrostatic attraction. This assumption is further supported by the fact that several polycations which reversibly and irreversibly bind cytochrome c peroxidase inhibit its enzymic activity in competition with ferrocytochrome c 17,62). 

The detailed chemical mechanism of the interaction between cytochrome c peroxidase and hydroperoxides to form Compound ES must be further elucidated. The use of substrate analogs such as various oxidiz-... 

Aniline, hydroxylation of, 150 Anilino-naphthalene sulfonate cytochrome c peroxidase and, 349, 359 transhydrogenase and, 69 Antimycin A... 

Arterial tissue, transhydrogenase in, 65 Ascites cells, glyoeraldehyde-3-phos-phate dehydrogenase in, 47 Ascorbate, cytochrome c peroxidase and, 353... 

Proteus vulgaris, sulfate reduction by, 281 Protoheme, cytochrome c peroxidase and, 345, 346, 348, 349... 

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