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Intermediate Tyrosyl Radical and Amyloid Structure in Peroxide-Activated Cytoglobin.

Ferreira JC, Marcondes MF, Icimoto MY, Cardoso TH, Tofanello A, Pessoto FS, Miranda EG, Prieto T, Nascimento OR, Oliveira V, Nantes IL - PLoS ONE (2015)

Bottom Line: When organic peroxides are used as substrates at initial reaction times, and given an excess of peroxide present, the EPR signals of the corresponding peroxyl radicals precede those of the direct tyrosyl radical.This result is consistent with the use of peroxide as a reducing agent for the recycling of Cygb high-valence species.This result suggests that Cygb possibly participates in the development of degenerative diseases; our findings also support the possible biological role of Cygb related to peroxidase activity.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Bioquímica, Universidade Federal de São Paulo, São Paulo, SP, Brazil.

ABSTRACT
We characterized the peroxidase mechanism of recombinant rat brain cytoglobin (Cygb) challenged by hydrogen peroxide, tert-butylhydroperoxide and by cumene hydroperoxide. The peroxidase mechanism of Cygb is similar to that of myoglobin. Cygb challenged by hydrogen peroxide is converted to a Fe4+ oxoferryl π cation, which is converted to Fe4+ oxoferryl and tyrosyl radical detected by direct continuous wave-electron paramagnetic resonance and by 3,5-dibromo-4-nitrosobenzene sulfonate spin trapping. When organic peroxides are used as substrates at initial reaction times, and given an excess of peroxide present, the EPR signals of the corresponding peroxyl radicals precede those of the direct tyrosyl radical. This result is consistent with the use of peroxide as a reducing agent for the recycling of Cygb high-valence species. Furthermore, we found that the Cygb oxidation by peroxides leads to the formation of amyloid fibrils. This result suggests that Cygb possibly participates in the development of degenerative diseases; our findings also support the possible biological role of Cygb related to peroxidase activity.

No MeSH data available.


Related in: MedlinePlus

Structure of tyrosyl radical in a protein polypeptide chain.In the structure it is indicated the rotation of phenoxyl radical around carbon β.
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pone.0136554.g005: Structure of tyrosyl radical in a protein polypeptide chain.In the structure it is indicated the rotation of phenoxyl radical around carbon β.

Mentions: The tyrosyl radical has an unpaired electron delocalized over the π ring and its EPR signal is determined by the hyperfine interaction with the four ring protons (Fig 5). Considering that the phenol group in the tyrosine structure can rotate around the Cβ-C1 bond, the EPR spectra of tyrosyl radical in proteins are extremely variable because of the different microenvironments caused by the protein chains [61,63,64].


Intermediate Tyrosyl Radical and Amyloid Structure in Peroxide-Activated Cytoglobin.

Ferreira JC, Marcondes MF, Icimoto MY, Cardoso TH, Tofanello A, Pessoto FS, Miranda EG, Prieto T, Nascimento OR, Oliveira V, Nantes IL - PLoS ONE (2015)

Structure of tyrosyl radical in a protein polypeptide chain.In the structure it is indicated the rotation of phenoxyl radical around carbon β.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4552303&req=5

pone.0136554.g005: Structure of tyrosyl radical in a protein polypeptide chain.In the structure it is indicated the rotation of phenoxyl radical around carbon β.
Mentions: The tyrosyl radical has an unpaired electron delocalized over the π ring and its EPR signal is determined by the hyperfine interaction with the four ring protons (Fig 5). Considering that the phenol group in the tyrosine structure can rotate around the Cβ-C1 bond, the EPR spectra of tyrosyl radical in proteins are extremely variable because of the different microenvironments caused by the protein chains [61,63,64].

Bottom Line: When organic peroxides are used as substrates at initial reaction times, and given an excess of peroxide present, the EPR signals of the corresponding peroxyl radicals precede those of the direct tyrosyl radical.This result is consistent with the use of peroxide as a reducing agent for the recycling of Cygb high-valence species.This result suggests that Cygb possibly participates in the development of degenerative diseases; our findings also support the possible biological role of Cygb related to peroxidase activity.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Bioquímica, Universidade Federal de São Paulo, São Paulo, SP, Brazil.

ABSTRACT
We characterized the peroxidase mechanism of recombinant rat brain cytoglobin (Cygb) challenged by hydrogen peroxide, tert-butylhydroperoxide and by cumene hydroperoxide. The peroxidase mechanism of Cygb is similar to that of myoglobin. Cygb challenged by hydrogen peroxide is converted to a Fe4+ oxoferryl π cation, which is converted to Fe4+ oxoferryl and tyrosyl radical detected by direct continuous wave-electron paramagnetic resonance and by 3,5-dibromo-4-nitrosobenzene sulfonate spin trapping. When organic peroxides are used as substrates at initial reaction times, and given an excess of peroxide present, the EPR signals of the corresponding peroxyl radicals precede those of the direct tyrosyl radical. This result is consistent with the use of peroxide as a reducing agent for the recycling of Cygb high-valence species. Furthermore, we found that the Cygb oxidation by peroxides leads to the formation of amyloid fibrils. This result suggests that Cygb possibly participates in the development of degenerative diseases; our findings also support the possible biological role of Cygb related to peroxidase activity.

No MeSH data available.


Related in: MedlinePlus