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Cited by 22Redox biology and oxidative stressFree Radicals and AntioxidantsElectron Spin Resonance Studies

Interactions of superoxide anion with enzyme radicals: Kinetics of reaction with lysozyme tryptophan radicals and corresponding effects on tyrosine electron transfer

Santus, René, Patterson, Larry K., Hug, Gordon L., Bazin, Marc, Mazière, Jean-Claude, Morlière, Patrice·2000·Free Radical Research
DOI 10.1080/10715760000300921
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Abstract

The kinetics of O2*- reaction with semi-oxidized tryptophan radicals in lysozyme, Trp*(Lyz) have been investigated at various pHs and conformational states by pulse radiolysis. The Trp*(Lyz) radicals were formed by Br2*- oxidation of the 3-4 exposed Trp residues in the protein. At pH lower than 6.2, the apparent bimolecular rate is about 2 x 10(8) M(-1) s(-1); but drops to 8 x 10(7) M(-1) s(-1) or less above pH 6.3 and in CTAC micelles. Similarly, the apparent bimolecular rate constant for the intermolecular Trp*(Lyz) + Trp*(Lyz) recombination reaction is about (4-7 x 10(6) M(-1) s(-1)) at/or below pH 6.2 then drops to 1.3-1.6 x 10(6) M(-1) s(-1) at higher pH or in micelles. This behavior suggests important conformational and/or microenvironmental rearrangement with pH, leading to less accessible semi-oxidized Trp* residues upon Br2*- reaction. The kinetics of Trp*(Lyz) with ascorbate, a reducing species rather larger than O2*- have been measured for comparison. The well-established long range intramolecular electron transfer from Tyr residues to Trp radicals--leading to the repair of the semi-oxidized Trp*(Lyz) and formation of the tyrosyl phenoxyl radical is inhibited by the Trp*(Lyz) + O2*- reaction, as is most of the Trp*(Lyz) + Trp*(Lyz) reaction. However, the kinetic behavior of Trp*(Lyz) suggests that not all oxidized Trp residues are involved in the intermolecular recombination or reaction with O2*-. As the kinetics are found to be quite pH sensitive, this study demonstrates the effect of the protein conformation on O2*- reactivity. To our knowledge, this is the first report on the kinetics of a protein-O2*- reaction not involving the detection of change in the redox state of a prosthetic group to probe the reactivity of the superoxide anion.

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  • Trp• reacts very rapidly with O2•− with second-order rate constants k in the range 0.7-2.2 × 10^9 M−1 s−1, mainly giving hydroperoxides in almost quantitative yields.

    “Trp• reacts very rapidly with O2•− with second order rate constants, k, in the range 0.7–2.2 × 109 M−1 s−1, the main initial products being hydroperoxides, in almost quantitative yields [145,146,147,148,149,150,151], Figure 56.”

    From Superoxide Anion Chemistry—Its Role at the Core of the Innate Immunity (2023) · cites this paper as [151]

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Authors
Santus, R., Patterson, L. K., Hug, G. L., Bazin, M., Mazière, J.-C., & Morlière, P.
Affiliations
  • Inserm (FR)
  • University of Notre Dame (US)
  • Muséum national d'Histoire naturelle (FR)
ORCID
Venue
Free Radical Research
Publisher
Informa UK Limited
Published
2000-01
Volume
33
Issue
4
Pages
383-391
ISSN
  • 1029-2470 (ISSN-L)
  • 1071-5762
DOI
10.1080/10715760000300921
OpenAlex
W2113296723
Cited by
22
References
26
Citations by year
2025: 1 · 2023: 1 · 2021: 1 · 2020: 1 · 2018: 2 · 2016: 1 · 2014: 1 · 2013: 2 · 2012: 1
FWCI
0.60
Type
journal article
Language
en
Open access
closed
Locations
  • Free Radical Research (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Redox biology and oxidative stress
  • Physical Sciences › Chemistry › Organic Chemistry › Free Radicals and Antioxidants
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biophysics › Electron Spin Resonance Studies
Keywords
superoxide, lysozyme, tryptophan radical, radical recombination kinetics, pH dependence, protein conformation, vitamin C, intramolecular electron transfer, protein oxidation
MeSH terms
Anions, Ascorbic Acid, Electron Transport, Free Radicals, Hydrogen-Ion Concentration, Kinetics, Micelles, Muramidase, Oxidation-Reduction, Oxygen, Pulse Radiolysis, Superoxides, Tryptophan, Tyrosine

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