How should xanthine oxidase-generated superoxide yields be measured?

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DOIResolve DOI: http://doi.org/10.1016/S0891-5849(00)00298-7
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TypeArticle
Journal titleFree Radical Biology and Medicine
ISSN0891-5849
Volume29
Issue5
Pages434441; # of pages: 8
Subjectacetaldehyde; cytochrome c oxidase; hydrogen peroxide; superoxide; tetranitromethane; xanthine oxidase; article; chemical analysis; chemical reaction; competitive inhibition; electron transport; priority journal; proton transport; reduction; Acetaldehyde; Animal; Comparative Study; Cytochrome c; Indicators and Reagents; Kinetics; Milk; Oxidation-Reduction; Spectrophotometry; Superoxides; Support, Non-U.S. Gov't; Tetranitromethane; Xanthine Oxidase
AbstractThe rate of formation of superoxide measured by its reduction of tetranitromethane (TNM) and by its reduction of ferric cytochrome c (Fe(III) cc) are in excellent agreement when the superoxide is generated from a simple chemical precursor. In contrast, the rate of formation of superoxide generated in the reaction of xanthine oxidase with acetaldehyde is much higher (up to a factor of 6) when measured with TNM and compared with Fe(III) cc. It is shown that Fe(III) cc measures superoxide that has diffused from the enzyme, and that TNM probably scavenges all the dioxygen that is reduced by one electron by the enzyme. The TNM traps enzyme-bound superoxide in competition with the second-electron transfer and proton transfer, which normally yield hydrogen peroxide. The proton transfer is probably rate determining, k(p) ≤ 3.8 x 103s-1. (C) 2000 Elsevier Science Inc.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21276687
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Record identifier417cf1e6-505f-4c1d-91ad-5741dd5b8c07
Record created2015-10-13
Record modified2016-05-09
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