Nitric oxide reversibly suppresses xanthine oxidase activity
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Updated: Sep 16, 2026

En Face Detection of Nitric Oxide and Superoxide in Endothelial Layer of Intact Arteries
Published on: February 25, 2016
M Fukahori1, K Ichimori, H Ishida
1Department of Physiology 2, School of Medicine, Tokai University, Kanagawa, Japan.
Abstract:
The effects of nitric oxide (NO) on xanthine oxidase (XOD) activity and the site(s) of the redox center(s) affected were investigated. XOD activity was determined by superoxide (O2-) generation and uric acid formation. NO reversibly and dose-dependently suppressed XOD activity in both determination methods. The suppression interval also disclosed a dose-dependent prolongation. The suppression occurred irrespective of the presence or absence of xanthine; indicating that the reaction product of NO and O2-, peroxynitrite, is not responsible for the suppression. Application of synthesized peroxynitrite did not affect XOD activity up to 2 microM. Methylene blue, which is an electron acceptor from Fe/S center, prevented the NO-induced inactivation. The results indicate that NO suppresses XOD activity through reversible alteration of the flavin prosthetic site.
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