کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1911204 1046806 2007 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Superoxide radical anions protect enkephalin from oxidation if the amine group is blocked
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی سالمندی
پیش نمایش صفحه اول مقاله
Superoxide radical anions protect enkephalin from oxidation if the amine group is blocked
چکیده انگلیسی

The pentapeptide methionine-enkephalin (Met-enk) is a natural opiate that inhibits signals of pain. The N-terminal tyrosyl residue is important in the recognition of the peptide by its receptor. In oxidative stress, this residue can be oxidized by reactive oxygen species. The one-electron oxidation of Met-enk and of tert-butoxycarbonyl-methionine-enkephalin (Boc-Met-enk) was studied by γ- and pulse radiolysis in the absence and in the presence of superoxide radical anions (O2−) and oxygen, using azidyl radicals as oxidants. Without oxygen, both peptides behaved similarly. The tyrosyl radical resulting from the oxidation of tyrosyl residue produced the dimer linked by dityrosines. Methionine was also oxidized to its sulfoxide; however, this reaction is of minor importance. When O2− was present, it added to tyrosyl radical giving a hydroperoxide. For Met-enk, this adduct cyclized via an intramolecular Michael addition of the amine on the aromatic ring. Conversely, for Boc-Met-enk, the adduct eliminated oxygen which led to 97% regeneration of the nonmodified peptide. Blocking the terminal amine group had thus a key role in protection of the tyrosyl residue. This finding might be exploited in the search for new pain inhibitors.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Free Radical Biology and Medicine - Volume 43, Issue 2, 15 July 2007, Pages 229–240
نویسندگان
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