Superoxide radicals react with peptide-derived tryptophan radicals with very high rate constants to give hydroperoxides as major products

Free Radical Biology & Medicine
Luke CarrollMichael J Davies

Abstract

Oxidative damage is a common process in many biological systems and proteins are major targets for damage due to their high abundance and very high rate constants for reaction with many oxidants (both radicals and two-electron species). Tryptophan (Trp) residues on peptides and proteins are a major sink for a large range of biological oxidants as these side-chains have low radical reduction potentials. The resulting Trp-derived indolyl radicals (Trp•) have long lifetimes in some circumstances due to their delocalized structures, and undergo only slow reaction with molecular oxygen, unlike most other biological radicals. In contrast, we have shown previously that Trp• undergo rapid dimerization. In the current study, we show that Trp• also undergo very fast reaction with superoxide radicals, O2•-, with k 1-2 × 109 M-1 s-1. These values do not alter dramatically with peptide structure, but the values of k correlate with overall peptide positive charge, consistent with positive electrostatic interactions. These reactions compete favourably with Trp• dimerization and O2 addition, indicating that this may be a major fate in some circumstances. The Trp• + O2•- reactions occur primarily by addition, rather than electron transfer, with...Continue Reading

Citations

Mar 29, 2019·Angewandte Chemie·Michael Hellwig
Dec 18, 2019·Essays in Biochemistry·Eduardo Fuentes-Lemus, Camilo López-Alarcón
Nov 2, 2019·The Journal of Biological Chemistry·Clare L Hawkins, Michael J Davies
Feb 6, 2020·Pharmaceutical Research·Christian Schöneich
Jun 27, 2019·Biochemistry. Biokhimii︠a︡·I I VlasovaV B Vasilyev
Aug 11, 2020·Free Radical Biology & Medicine·Camilo López-AlarcónMichael J Davies
Sep 11, 2020·Free Radical Biology & Medicine·Stephanie BellmaineAline Zimmer
Mar 18, 2021·Antioxidants & Redox Signaling·Marilene DemasiLeonor Thomson

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