Characterization of the Effects of Oxygen on Xanthine Oxidase-mediated Nitric Oxide Formation

Haitao Li, Alexandre Samouilov, Xiaoping Liu, Jay L. Zweier

Research output: Contribution to journalArticle

Abstract

Under anaerobic conditions, xanthine oxidase (XO)-catalyzed nitrite reduction can be an important source of nitric oxide (NO). However, questions remain regarding whether significant XO-mediated NO generation also occurs under aerobic conditions. Therefore, electron paramagnetic resonance, chemiluminescence NO-analyzer, and NO-electrode studies were performed to characterize the kinetics and magnitude of XO-mediated nitrite reduction as a function of oxygen tension. With substrates xanthine or 2,3-dihydroxybenz-aldehyde that provide electrons to XO at the molybdenum site, the rate of NO production followed Michaelis-Menten kinetics, and oxygen functioned as a competitive inhibitor of nitrite reduction. However, with flavin-adenine dinucleotide site-binding substrate NADH as electron donor, aerobic NO production was maintained at more than 70% of anaerobic levels, and binding of NADH to the flavin-adenine dinucleotide site seemed to prevent oxygen binding. Therefore, under aerobic conditions, NADH would be the main electron donor for XO-catalyzed NO production in tissues. Studies of the pH dependence of NO formation indicated that lower pH values decrease oxygen reduction but greatly increase nitrite reduction, facilitating NO generation. Isotope tracer studies demonstrated that XO-mediated NO formation occurs in normoxic and hypoxic heart tissue. Thus, XO-mediated NO generation occurs under aerobic conditions and is regulated by oxygen tension, pH, nitrite, and reducing substrate concentrations.

Original languageEnglish (US)
Pages (from-to)16939-16946
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number17
DOIs
StatePublished - Apr 23 2004
Externally publishedYes

Fingerprint

Xanthine Oxidase
Nitric Oxide
Oxygen
Nitrites
NAD
Flavin-Adenine Dinucleotide
Electrons
Substrates
Tissue
Xanthine
Molybdenum
Nitric Oxide Donors
Kinetics
Electron Spin Resonance Spectroscopy
Chemiluminescence
Luminescence
Aldehydes
Isotopes
Electrodes
Paramagnetic resonance

ASJC Scopus subject areas

  • Biochemistry

Cite this

Characterization of the Effects of Oxygen on Xanthine Oxidase-mediated Nitric Oxide Formation. / Li, Haitao; Samouilov, Alexandre; Liu, Xiaoping; Zweier, Jay L.

In: Journal of Biological Chemistry, Vol. 279, No. 17, 23.04.2004, p. 16939-16946.

Research output: Contribution to journalArticle

Li, Haitao ; Samouilov, Alexandre ; Liu, Xiaoping ; Zweier, Jay L. / Characterization of the Effects of Oxygen on Xanthine Oxidase-mediated Nitric Oxide Formation. In: Journal of Biological Chemistry. 2004 ; Vol. 279, No. 17. pp. 16939-16946.
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