Production of the carbonate radical anion during xanthine oxidase turnover in the presence of bicarbonate. J Biol Chem 2004 Dec 10;279(50):51836-43
Date
09/28/2004Pubmed ID
15448145DOI
10.1074/jbc.M406929200Scopus ID
2-s2.0-10644245807 (requires institutional sign-in at Scopus site) 81 CitationsAbstract
Xanthine oxidase is generally recognized as a key enzyme in purine catabolism, but its structural complexity, low substrate specificity, and specialized tissue distribution suggest other functions that remain to be fully identified. The potential of xanthine oxidase to generate superoxide radical anion, hydrogen peroxide, and peroxynitrite has been extensively explored in pathophysiological contexts. Here we demonstrate that xanthine oxidase turnover at physiological pH produces a strong one-electron oxidant, the carbonate radical anion. The radical was shown to be produced from acetaldehyde oxidation by xanthine oxidase in the presence of catalase and bicarbonate on the basis of several lines of evidence such as oxidation of both dihydrorhodamine 123 and 5,5-dimethyl-1-pyrroline-N-oxide and chemiluminescence and isotope labeling/mass spectrometry studies. In the case of xanthine oxidase acting upon xanthine and hypoxanthine as substrates, carbonate radical anion production was also evidenced by the oxidation of 5,5-dimethyl-1-pyrroline-N-oxide and of dihydrorhodamine 123 in the presence of uricase. The results indicated that Fenton chemistry occurring in the bulk solution is not necessary for carbonate radical anion production. Under the conditions employed, the radical was likely to be produced at the enzyme active site by reduction of a peroxymonocarbonate intermediate whose formation and reduction is facilitated by the many xanthine oxidase redox centers. In addition to indicating that the carbonate radical anion may be an important mediator of the pathophysiological effects of xanthine oxidase, the results emphasize the potential of the bicarbonate-carbon dioxide pair as a source of biological oxidants.
Author List
Bonini MG, Miyamoto S, Di Mascio P, Augusto OMESH terms used to index this publication - Major topics in bold
AnimalsBicarbonates
Carbonates
Catalytic Domain
Cattle
Cyclic N-Oxides
Electron Spin Resonance Spectroscopy
Free Radicals
Hydrogen-Ion Concentration
In Vitro Techniques
Models, Biological
Oxidation-Reduction
Rhodamines
Spin Labels
Substrate Specificity
Xanthine Oxidase
