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Nitric oxide reversibly suppresses xanthine oxidase activity
M Fukahori1, K Ichimori, H Ishida
1Department of Physiology 2, School of Medicine, Tokai University, Kanagawa, Japan.
Free Radical Research
|September 1, 1994
Summary
Nitric oxide (NO) reversibly suppresses xanthine oxidase (XOD) activity by altering its flavin prosthetic site. This finding clarifies the mechanism of NO
Area of Science:
- Biochemistry
- Enzymology
- Redox Biology
Background:
- Xanthine oxidase (XOD) is a key enzyme in purine metabolism.
- Nitric oxide (NO) is a critical signaling molecule with diverse biological roles.
- The interaction between NO and XOD activity requires further elucidation.
Purpose of the Study:
- To investigate the effects of nitric oxide (NO) on xanthine oxidase (XOD) activity.
- To identify the specific redox center(s) affected by NO within XOD.
Main Methods:
- XOD activity was measured by quantifying superoxide (O2-) generation and uric acid formation.
- The influence of NO was assessed in a dose-dependent manner.
- Methylene blue was used to probe the role of the Fe/S center.
Main Results:
- Nitric oxide (NO) reversibly and dose-dependently suppressed XOD activity.
- Suppression occurred independently of xanthine, ruling out peroxynitrite as the causative agent.
- Methylene blue prevented NO-induced inactivation, implicating the Fe/S center's electron transfer.
Conclusions:
- Nitric oxide (NO) suppresses xanthine oxidase (XOD) activity.
- The suppression is mediated by a reversible alteration of the flavin prosthetic site.
- This interaction provides new insights into the regulation of XOD by NO.