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Recycling of the high valence States of heme proteins by cysteine residues of THIMET-oligopeptidase.

Ferreira JC, Icimoto MY, Marcondes MF, Oliveira V, Nascimento OR, Nantes IL - PLoS ONE (2013)

Bottom Line: The TOP-promoted recycling of the high valence states of the peroxidases to the respective resting form was accompanied by a significant decrease in the thiol content of the peptidolytic enzyme.The oxidation of TOP thiol groups by peroxidases did not promote the inactivating oligomerization observed in the oxidation promoted by the enzyme aging.These findings are discussed towards a possible occurrence of these reactions in cells.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brasil ; Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo Andre, SP, Brasil.

ABSTRACT
The peptidolytic enzyme THIMET-oligopeptidase (TOP) is able to act as a reducing agent in the peroxidase cycle of myoglobin (Mb) and horseradish peroxidase (HRP). The TOP-promoted recycling of the high valence states of the peroxidases to the respective resting form was accompanied by a significant decrease in the thiol content of the peptidolytic enzyme. EPR (electron paramagnetic resonance) analysis using DBNBS spin trapping revealed that TOP also prevented the formation of tryptophanyl radical in Mb challenged by H2O2. The oxidation of TOP thiol groups by peroxidases did not promote the inactivating oligomerization observed in the oxidation promoted by the enzyme aging. These findings are discussed towards a possible occurrence of these reactions in cells.

Show MeSH
Production of TOP thiyl radical by Mb.The Mb-catalized one-electron oxidation of TOP is expected to generate thiyl free radical and the fate of this free radical is proposed according to reference 55.
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pone-0079102-g010: Production of TOP thiyl radical by Mb.The Mb-catalized one-electron oxidation of TOP is expected to generate thiyl free radical and the fate of this free radical is proposed according to reference 55.

Mentions: In the presence of TOP (Figure 9), steps a and b also occurs, but the Mb “Compound I” is recycled to the resting form by using TOP thiol groups as a reducing agent (steps c and d). The percentage of “Compound I” recycled to the resting form by two one-electron oxidation steps (c and d) is dependent on TOP concentration. The Mb-catalized one-electron oxidation of TOP is expected to generate thiyl free radical and the fate of this free radical is proposed in Figure 10. The electrophoresis gel obtained after oxidation of 40% and 100% reduced TOP showed that oxidative oligomerization is not favored in this condition. Therefore, thiyl radicals may react with molecular oxygen generating sulfinic acid and other radical products.


Recycling of the high valence States of heme proteins by cysteine residues of THIMET-oligopeptidase.

Ferreira JC, Icimoto MY, Marcondes MF, Oliveira V, Nascimento OR, Nantes IL - PLoS ONE (2013)

Production of TOP thiyl radical by Mb.The Mb-catalized one-electron oxidation of TOP is expected to generate thiyl free radical and the fate of this free radical is proposed according to reference 55.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3815109&req=5

pone-0079102-g010: Production of TOP thiyl radical by Mb.The Mb-catalized one-electron oxidation of TOP is expected to generate thiyl free radical and the fate of this free radical is proposed according to reference 55.
Mentions: In the presence of TOP (Figure 9), steps a and b also occurs, but the Mb “Compound I” is recycled to the resting form by using TOP thiol groups as a reducing agent (steps c and d). The percentage of “Compound I” recycled to the resting form by two one-electron oxidation steps (c and d) is dependent on TOP concentration. The Mb-catalized one-electron oxidation of TOP is expected to generate thiyl free radical and the fate of this free radical is proposed in Figure 10. The electrophoresis gel obtained after oxidation of 40% and 100% reduced TOP showed that oxidative oligomerization is not favored in this condition. Therefore, thiyl radicals may react with molecular oxygen generating sulfinic acid and other radical products.

Bottom Line: The TOP-promoted recycling of the high valence states of the peroxidases to the respective resting form was accompanied by a significant decrease in the thiol content of the peptidolytic enzyme.The oxidation of TOP thiol groups by peroxidases did not promote the inactivating oligomerization observed in the oxidation promoted by the enzyme aging.These findings are discussed towards a possible occurrence of these reactions in cells.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brasil ; Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo Andre, SP, Brasil.

ABSTRACT
The peptidolytic enzyme THIMET-oligopeptidase (TOP) is able to act as a reducing agent in the peroxidase cycle of myoglobin (Mb) and horseradish peroxidase (HRP). The TOP-promoted recycling of the high valence states of the peroxidases to the respective resting form was accompanied by a significant decrease in the thiol content of the peptidolytic enzyme. EPR (electron paramagnetic resonance) analysis using DBNBS spin trapping revealed that TOP also prevented the formation of tryptophanyl radical in Mb challenged by H2O2. The oxidation of TOP thiol groups by peroxidases did not promote the inactivating oligomerization observed in the oxidation promoted by the enzyme aging. These findings are discussed towards a possible occurrence of these reactions in cells.

Show MeSH