title: Nitric oxide reversibly suppresses xanthine oxidase activity.
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.
authors: Department of Physiology 2, School of Medicine, Tokai University, Kanagawa, Japan.
authors: M
authors: M
authors: Fukahori
authors: K
authors: K
authors: Ichimori
authors: H
authors: H
authors: Ishida
authors: H
authors: H
authors: Nakagawa
authors: H
authors: H
authors: Okino
mesh_terms: D004789:Enzyme Activation / Q000187:drug effects; D009569:Nitric Oxide / Q000494:pharmacology*; D010084:Oxidation-Reduction; D013054:Spectrophotometry, Atomic; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors* / Q000737:chemistry
chemical_list: D009569:Nitric Oxide; D014969:Xanthine Oxidase