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Peroxidase Compound

Rodrfguez-Lopez, J.N., Gilabert, M.A., Tudela, J., Thorneley, R.N.R, and Garcfa-Canovas, R, Reactivity of horseradish peroxidase compound II toward substrates kinetic evidence for a two-step mechanism,... [Pg.686]

Gosh, A., J. Almlof, and L. Que Jr. 1994. Density Functional Theoretical Study of Oxo(porphyroinato)iron(IV) Complexes, Models of Peroxidase Compounds I and II. J. Phys. Chem. 98, 5576. [Pg.125]

Figure 5. Comparison of the optical absorption spectra of cobalt(III) porphyrin ir-cation radical species with those of catalase compound / and horseradish peroxidase compound L The ground states of the bromide and perchlorate species are 2A lu and 2Agu, respectively. Figure 5. Comparison of the optical absorption spectra of cobalt(III) porphyrin ir-cation radical species with those of catalase compound / and horseradish peroxidase compound L The ground states of the bromide and perchlorate species are 2A lu and 2Agu, respectively.
The rate constants of kn and kx obtained using Eq. (24) reveal that (i) the activity of Fem-TAMLs in bleaching Safranine O (k ) increases more than 10-fold when the tail ethyl groups of la are replaced by fluorine atoms in lk. The rate constant kn for lk equals l(rM 1s 1 at 25°C, a value that corresponds to those found for the reactivity of horseradish peroxidase Compound II... [Pg.512]

Several compounds can be oxidized by peroxidases by a free radical mechanism. Among various substrates of peroxidases, L-tyrosine attracts a great interest as an important phenolic compound containing at 100 200 pmol 1 1 in plasma and cells, which can be involved in lipid and protein oxidation. In 1980, Ralston and Dunford [187] have shown that HRP Compound II oxidizes L-tyrosine and 3,5-diiodo-L-tyrosine with pH-dependent reaction rates. Ohtaki et al. [188] measured the rate constants for the reactions of hog thyroid peroxidase Compounds I and II with L-tyrosine (Table 22.1) and showed that Compound I was reduced directly to ferric enzyme. Thus, in this case the reaction of Compound I with L-tyrosine proceeds by two-electron mechanism. In subsequent work these authors have shown [189] that at physiological pH TPO catalyzed the two-electron oxidation not only L-tyrosine but also D-tyrosine, A -acetyltyrosinamide, and monoiodotyrosine, whereas diiodotyrosine was oxidized by a one-electron mechanism. [Pg.734]

However, in addition to two-electron oxidation by native peroxidase, Compound I can oxidize hydrogen peroxide by one-electron mechanism ... [Pg.737]

The form of the enzyme with the greatest oxidation potential is known as horseradish peroxidase, compound 1 (HRP-I), which consists of a radical cation stabilized throughout the highly conjugated protoporphyrin IX ring system. In the presence of vindoline, HRP-I is reduced to HRP-H, an Fe(IV) form of the enzyme. The vindoline cation radical 55 thus formed eliminates a second elec-... [Pg.370]

Fig. 7. Catalatic and peroxidatic reactions of type B enzymes. This represents a modification of the schemes of Figs. 2 and 5A and is proposed to account for the characteristic features of catalase-peroxidases. Compound I is drawn as Fe +=0 and can represent either a -rr-cation radical or alternative radical structure. The precise nature remains undefined (see Section IV,F). Fig. 7. Catalatic and peroxidatic reactions of type B enzymes. This represents a modification of the schemes of Figs. 2 and 5A and is proposed to account for the characteristic features of catalase-peroxidases. Compound I is drawn as Fe +=0 and can represent either a -rr-cation radical or alternative radical structure. The precise nature remains undefined (see Section IV,F).
Once the oxy complex is formed, a second electron transfer to the HO heme effectively reduces the oxy complex to the peroxide level. From this point many heme enzymes catalyze the heterolytic fission of the peroxide 0-0 bond, leaving behind the well known oxyferryl center, (Fe-0) +, characteristic of peroxidase compound 1 and similar to the active hydroxylating intermediate thought to operate in P450s. However, in HO the active oxidizing intermediate is peroxide. Peracids that form the (Fe-0) + intermediate do not support the HO reaction, whereas H2O2 addition to Fe + HO does support substrate hydroxylation 187, 188). EPR and ENDOR spectroscopy have been used to analyze the cryo-genically reduced oxy-HO complex 189). In these studies reduction of... [Pg.281]

Although compound I formation is not influenced by pH, reactions of compounds I and II are significantly affected by pH. These reactions are acid-catalyzed 16,17). The rate constant for the oxidation of veratryl alcohol or fenocyanide by lignin peroxidase compound I is 10 times greater at pH 3.5 than at pH 6.0. The enhancement in rate is of the same magnitude for compound II reacting with veratryl alcohol. Therefore, the observed pH dependency for Vmax in catalysis is due to the pH-dependent reactions between the compounds I and n and the reducing substrates. [Pg.182]

Formation and Structure of Oxycomplex. Compound III is formed when peroxidase is incubated with excess H2O2 (12). The structure of peroxidase compound HI has been well established as the oxygenated form of ferroperoxidase (Fe2+02), the same as oxymyoglobin. Therefore, it is more accurately referred to as the oxycomplex. [Pg.182]

However, the distal histidine apparently has no effect on lignin and Mn-dependent peroxidase compound I formation. Although all active site amino acid residues that are proposed to participate in compound I formation of peroxidase (37) are conserved in lignin and Mn-dependent pa oxidases, the lack of pH dependence may be a result of some inherent structural and conformational differences between lignin and Mn-dependent peroxidases and other peroxidases. [Pg.186]

The aims of this study were to observe isotropically shifted signals for metal ions like copper(II), which usually give signals broadened beyond detection, and to relate the observed shifts and relaxation times to those of the uncoupled ions in order to understand the phenomena in theoretical terms. This approach allows the power of the NMR technique to fully exploit paramagnetic species and obtain information on spin delocalization, chemical bonding and so on. It is likely that the theory also applies to coupled metal ion-H adical systems like those proposed for derivatives of peroxidases (compound I), which contain iron(IV) and a heme radical (44). [Pg.80]

HOPhjSil O, 42 214 Horseradish peroxidase compound I formation, 43 97-98 endogenous reduction of intermediates, 43 100... [Pg.135]

Tyrosyl radical Fe(TV)Tyr is formed by an internal electron transfer in the peroxidase Compound I ... [Pg.815]

As for the peroxidases, Compound I and water are formed in the first step from one equivalent of hydrogen peroxide and the resting state of the catalase. The back-reaction, however, does not proceed via Compound II but rather via a two-electron-two-proton transfer cascade, in which both hydrogen atoms of a second molecule of hydrogen peroxide are transferred to the ferryl subunit of the porphyrin cofactor. Due to the similarity of catalases and peroxidases, it is not too surprising that this reaction is also catalyzed by most peroxidases. Alternatively, catalases and some peroxidases react with alkyl hydroperoxides via the respective alkanol to an aldehyde or ketone (Scheme 2.17). A requirement for this reaction is an easily accessible active site for the hydroperoxide, so that only those peroxidases with open access such as CPO or CiP are able to promote this reaction. [Pg.59]

Khindaria A, Nie G, Aust SD (1997) Detection and characterization of the lignin peroxidase compound II- veratryl alcohol cation radical complex. Biochemistry 36 14181-14185... [Pg.58]


See other pages where Peroxidase Compound is mentioned: [Pg.406]    [Pg.70]    [Pg.459]    [Pg.814]    [Pg.361]    [Pg.128]    [Pg.152]    [Pg.21]    [Pg.23]    [Pg.32]    [Pg.383]    [Pg.9]    [Pg.69]    [Pg.38]    [Pg.855]    [Pg.836]    [Pg.128]    [Pg.582]    [Pg.283]    [Pg.332]    [Pg.334]    [Pg.336]    [Pg.340]    [Pg.184]    [Pg.69]    [Pg.69]    [Pg.69]    [Pg.69]    [Pg.69]   
See also in sourсe #XX -- [ Pg.853 , Pg.854 ]

See also in sourсe #XX -- [ Pg.853 , Pg.854 ]

See also in sourсe #XX -- [ Pg.374 , Pg.375 , Pg.376 , Pg.377 , Pg.380 , Pg.384 ]

See also in sourсe #XX -- [ Pg.853 , Pg.854 ]

See also in sourсe #XX -- [ Pg.853 , Pg.854 ]




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Compound I of horseradish peroxidase

Compound I of peroxidase

Conversion peroxidase compounds

Horseradish peroxidase compound

Horseradish peroxidase compound I formation

Horseradish peroxidase compound oxidation

Peroxidase-hydrogen peroxide compound

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