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1

Kinetic studies on the oxidation of nitrite by horseradish peroxidase and lactoperoxidase

100%
Gebicka L.
Acta Biochimica Polonica
|
1999
|
tom 46
|
nr 4
The reaction of nitrite (NO-2) with horseradish peroxidase and lactoperoxidase was studied. Sequential mixing sopped-flow measeruments gave the following values for the rate constants of the reaction of nitrite with compounds II (oxoferryl heme intermediates) of horseradish peroxidase and lactoperoxidase at pH 7.0, 13.3 ± 0.07 mol-1dm3s-1 and 3.5 ± 0.05 · 104mol-1dm3s-1, respectively. Nitrite, at neutral pH, influenced measurements of activity of lactoperoxidase with typical substrates like 2,2'-azino-bis[ethyl-benzothiazoline-(6)-sulphonic acid] (ABTS), guaiacol or thiocyanate (SCN-). The rate of ABTS and guaiacol oxidation increased linearly with nitrite concentration up to 2.5-5 mmol dm-3. On the other hand, two-electron SCN- oxidation was inhibited in the presence od nitrite. Thus, nitrite competed with the investigated substrates of lactoperoxidase. The intermediate, most probably nitrogen dioxide (*NO2), reacted more rapidly with ABTS or guaiacol than did lactoperoxidase compound II. It did not, however, effectively oxidize SCN- to OSCN-. NO-2 did not influence the activity measurements of horseradish peroxidase by ABTS or guaiacol method.
2

Mechanism of peroxynitrite interaction with cytochrome c

63%
Gebicka L., Didik J.
Acta Biochimica Polonica
|
2003
|
tom 50
|
nr Supplement 1
3

Catalytic properties of heme peroxidases in microheterogeneous systems

63%
Jurgas-Grudzinska M., Gebicka L.
Acta Biochimica Polonica
|
2006
|
tom 53
|
nr Supplement 1
4

Nadtlenoazotyn jako czynnik wywołujący stres oksydacyjny

63%
Gebicka L., Didik J.
Postępy Biochemii
|
2010
|
tom 56
|
nr 2
5

Flavonoids as reductants of ferryl hemoglobin

63%
Gebicka L., Banasiak E.
Acta Biochimica Polonica
|
2009
|
tom 56
|
nr 3
509-513
The ferryl derivatives of hemoglobin are products of the reactions of oxy- and methemoglobin with hydrogen peroxide. Ferryl hemoglobins, either with or without a radical site on the protein moiety, are oxidizing species. Plant polyphenols, flavonoids, have been shown to act as antioxidants in vivo and in vitro. Reactions of met- and oxyhemoglobin with hydrogen peroxide in the presence of catechin, quercetin and rutin were studied. These flavonoids accelerated reduction of ferryl hemoglobin to methemoglobin. The rate constants of the reactions of ferryl hemoglobin with catechin, quercetin and rutin were in the order of 102 M-1 s-1, i.e. similar to the rate constants of ferryl hemoglobin with intracellular reducing compounds like urate or ascorbate. The beneficial effect of flavonoids against oxidative damage of hemoglobin caused by hydroperoxides, reported in the literature, is probably, at least in part, connected with the ability of flavonoids to scavenge ferryl hemoglobin.
6

Reactions of oxygen radicals with heme peroxidases

63%
Gebicka L., Gebicki J. L.
Current Topics in Biophysics
|
1994
|
tom 18
|
nr 2
7

Does the peroxidase-like activity of sodium dodecyl sulphate-modified cytochrome c increase after peroxynitrite or radiation treatment?

63%
Gebicka L., Didik J.
Acta Biochimica Polonica
|
2005
|
tom 52
|
nr 2
The peroxidase-like activity of cytochrome c is considerably increased by unfolding of the protein. The enhancement of the activity is due to the higher reaction rate of unfolded cytochrome c with hydrogen peroxide, which is the rate-determining step in the peroxidase cycle of cytochrome c (Gębicka, L., 2001, Res Chem Intermed 27, 717–23). In this study we checked whether combined action of two unfolding factors, SDS and peroxynitrite or radiation (hydroxyl radicals), increases the peroxidase-like activity of cytochrome c more than any single treatment alone. Peroxynitrite reacts with SDS-modified cytochrome c in the same way as with native cytochrome c, via intermediate radical products, •OH/•NO2, arising from peroxynitrite homolysis. We found that SDS-modified cytochrome c is much more sensitive to oxidative damage than the native protein. Partial unfolding of cytochrome c by SDS causes the peroxide substrate to have a better access to the heme center. On the other hand, the amino acids located in the vicinity of the active site and/or heme group become accessible for oxidizing radicals. The overall effect observed is that the peroxidase-like activity of SDS-modified cytochrome c decreases with an increase of the concentration of the oxidizing species (peroxynitrite or radiolytically generated hydroxyl radicals). The damage of SDS-modified cytochrome c caused by irradiation is much more significant than that observed after peroxynitrite treatment.
8

Scavenging of oxygen radicals by heme peroxidases

63%
Gebicka L., Gebicki J. L.
Acta Biochimica Polonica
|
1996
|
tom 43
|
nr 4
The reactions of two heme peroxidases, horseradish peroxidase and lactoperoxidase and their compounds II (oxoferryl heme intermediates, Fe(IV)=0 or ferric protein radical Fe(III)R') and compounds III (resonance hybrids [Fe(IIIK)2 «-» Fe(II)-02l with superoxide radical anion generated enzymatically or radiolytically, and with hydroxyl radicals generated radiolytically, were investigated. It is suggested that only the protein radical form of compound II of lactoperoxidase reacts with superoxide, whereas compound II of horseradich peroxidase, which exists only in oxoferryl form, is unreactive towards superoxide. Compound III of the investigated peroxidases does not react with superoxide. The lactoperoxidase activity loss induced by hydroxyl radicals is closely related to the loss of the ability to form compound I (oxoferryl porphyrin n-cation radical, Fed V)=0(Por+) or oxoferryl protein radical Fe(IV)=0(R )). On the other hand, the modification of horseradish peroxidase induced by hydroxyl radicals has been reported to cause also restrictions in substrate binding (Gębicka, L. & Gębicki, J.L., 1996, Biochimie 78,62-65). Nevertheless, it has been found that only a small fraction of hydroxyl radicals generated homogeneously does inactivate the enzymes.
9

Mechanism of peroxynitrite interaction with cytochrome C

63%
Gebicka L., Didik J.
Acta Biochimica Polonica
|
2003
|
tom 50
|
nr 3
Kinetics of the reaction of peroxynitrite with ferric cytochrome c in the absence and presence of bicarbonate was studied. It was found that the heme iron in ferric cytochrome c does not react directly with peroxynitrite. The rates of the absorbance changes in the Soret region of cytochrome c spectrum caused by peroxynitrite or peroxynitrite/bicarbonate were the same as the rate of spontaneous isomerization of peroxynitrite or as the rate of the reaction of peroxynitrite with bicarbonate, respec­tively. This means that intermediate products of peroxynitrite decomposition, OH/ NO2 or, in the presence of bicarbonate, CO3- / NO2, are the species responsible for the absorbance changes in the Soret band of cytochrome c. Modifications of the heme center of cytochrome c by radiolytically produced radicals, OH, NO2 or CO3- , were also studied. The absorbance changes in the Soret band caused by radiolytically produced OH or CO3- were much more significant that those observed after peroxy­nitrite treatment, compared under similar concentrations of radicals. NO2 produced radiolytically did not interact with the heme center of cytochrome c. Cytochrome c ex­hibited an increased peroxidase-like activity after reaction with peroxynitrite as well as with radiolytically produced OH, NO2 or CO3- radicals. This means that modifi­cation of protein structure: oxidation of amino acids and/or tyrosine nitration, facili­tates reaction of H2O2 with the heme iron of cytochrome c, followed by reaction with the second substrate.
10

Reactions of heme proteins with peroxynitrate

51%
Gebicka L., Gebicka J. L., Didik J.
Acta Biochimica Polonica
|
2006
|
tom 53
|
nr Supplement 1
11

Reactions of peroxynitrite-derived carbonate and nitrogen dioxide radical with heme peroxidases

51%
Didik J., Gebicki J. L., Gebicka L.
Acta Biochimica Polonica
|
2006
|
tom 53
|
nr Supplement 1
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