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Updated: Jul 14, 2026

Rapid Quantification of Oxidized and Reduced Forms of Glutathione Using Ortho -phthalaldehyde in Cultured Mammalian Cells In Vitro
Published on: June 28, 2024
The glutathione thiyl radical does not react with nitrogen monoxide.
Dustin Hofstetter1, Thomas Nauser, Willem H Koppenol
1Laboratory for Inorganic Chemistry, Department of Chemistry and Applied Bioscience, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland.
The reaction between glutathione thiyl radicals and nitrogen monoxide is slower than previously thought. Under physiological conditions, the thiyl radical converts to a carbon-centred form, limiting S-nitrosoglutathione production.
Area of Science:
- Biochemistry
- Chemical Kinetics
- Free Radical Chemistry
Background:
- Glutathione (GSH) is a key cellular antioxidant.
- Nitrogen monoxide (NO) plays diverse physiological roles.
- S-nitrosoglutathione (GSNO) is a biologically relevant S-nitrosothiol.
Purpose of the Study:
- To determine the rate constant for the reaction between the glutathione thiyl radical and nitrogen monoxide.
- To assess the physiological relevance of GSNO formation under varying NO concentrations.
Main Methods:
- Laser flash photolysis was employed to generate and study the glutathione thiyl radical.
- Kinetic measurements were performed to quantify reaction rates.
Main Results:
- The rate constant for the reaction of the glutathione thiyl radical with nitrogen monoxide to form GSNO was determined to be less than 2.8 ± 0.6 x 10(7) M(-1)s(-1).
- At physiological NO concentrations, the conversion of the thiyl radical to its carbon-centred form (at rates of 10(3) s(-1)) was found to be faster than GSNO formation.
Conclusions:
- The determined rate constant suggests a less efficient pathway for GSNO formation than previously estimated.
- Cellular conditions may favor alternative reactions of the glutathione thiyl radical over GSNO synthesis.
- This finding has implications for understanding redox signaling and oxidative stress involving glutathione and NO.
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