Nitric Oxide Reversibly Suppresses Xanthine Oxidase Activity |
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Authors: | Masami Fukahori Kohji Ichimori Hideyuki Ishida Hiroe Nakagawa Haruka Okino |
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Affiliation: | a Department of Physiology 2, School of Medicine, Tokai University, Bohseidai, Isehara, Kanagawa, Japan |
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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 μM. 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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Keywords: | Xanthine oxidase Nitric oxide Methylene blue FAD |
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