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Enzyme inactivation through sulfhydryl oxidation by physiologic NO-carriers
K Becker1, S N Savvides, M Keese
1Biochemistry Center, University of Heidelberg, Germany. katja.becker@urz.uni-heidelberg.de
Nitric oxide (NO) inactivates human glutathione reductase (hGR) by oxidizing cysteine residues. Different NO carriers cause distinct chemical modifications, revealing sulfhydryl oxidation as a key NO mechanism.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Nitric oxide (NO) is a crucial signaling molecule with largely unknown molecular mechanisms.
- Identifying and characterizing NO's physiological targets and their modifications are essential.
- Human glutathione reductase (hGR) is vital for cellular antioxidant defense.
Purpose of the Study:
- To elucidate the molecular mechanisms of enzyme inactivation by nitric oxide (NO) carriers.
- To characterize the specific chemical modifications of human glutathione reductase (hGR) by NO.
- To understand how different NO forms mediate distinct chemical reactions.
Main Methods:
- Determined crystal structures of hGR inactivated by S-nitrosoglutathione (GSNO) and diglutathionyl-dinitroso-iron (DNIC-[GSH]2) at 1.7 A resolution.
- Analyzed the active site modifications in GSNO- and DNIC-[GSH]2-treated hGR.
Main Results:
- GSNO modification resulted in oxidation of Cys 63 to cysteine sulfenic acid (R-SOH).
- DNIC-[GSH]2 modification led to oxidation of Cys 63 to cysteine sulfinic acid (R-SO2H).
- These structures provide the first atomic-level view of enzyme inactivation by NO carriers.
Conclusions:
- Different nitric oxide (NO) carriers mediate distinct chemical reactions.
- Sulfhydryl oxidation of cysteine residues is a major mechanism by which NO exerts its effects.
- These findings advance our understanding of NO signaling and enzyme regulation.
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