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Hydrogen peroxide modification of human oxyhemoglobin.
1Department of Biochemistry, Wake Forest University Medical Center, Bowman Gray School of Medicine, Winston-Salem, North Carolina 27103.
Free Radical Research Communications
|January 1, 1991
Summary
Hydrogen peroxide (H2O2) modifies hemoglobin (Hb) structures. The heme group in oxyhemoglobin (OxyHb) is crucial for H2O2-induced tryptophan modification in its beta-chain.
Area of Science:
- Biochemistry
- Protein Chemistry
- Oxidative Stress
Background:
- Hemoglobin (Hb) is a vital protein responsible for oxygen transport.
- Oxidative modifications of Hb can impact its function and lead to various pathologies.
- Hydrogen peroxide (H2O2) is a reactive oxygen species implicated in oxidative damage.
Purpose of the Study:
- To investigate the effects of H2O2 on the primary structure of oxyhemoglobin (OxyHb) and apomyoglobin (ApoHb).
- To elucidate the specific amino acid residues modified by H2O2 in both heme-bound and heme-free Hb.
- To determine the role of the heme moiety and potential metal catalysis in H2O2-mediated modifications.
Main Methods:
- Treatment of OxyHb and ApoHb with H2O2 at a defined molar ratio ([Heme]/[H2O2] = 1).
- Analysis of primary protein structure to identify modified amino acid residues.
- Investigation of reaction mechanisms, including direct oxidation and metal-catalyzed oxidation.
Main Results:
- In OxyHb, H2O2 treatment (1:1 ratio) modified tryptophan and methionine residues in the beta-chain.
- In ApoHb, H2O2 treatment modified histidine and methionine residues in both globin chains; tryptophan residues remained unaffected.
- Methionine modification likely resulted from direct H2O2 oxidation, while histidine modification in ApoHb suggested metal-catalyzed oxidation involving iron.
- Tryptophan modification in OxyHb's beta-chain was dependent on the presence of the heme moiety.
Conclusions:
- H2O2 induces distinct structural modifications in hemoglobin depending on the presence of the heme group.
- The heme moiety plays a critical role in mediating H2O2-induced tryptophan oxidation in OxyHb.
- Methionine residues are susceptible to direct oxidation by H2O2, irrespective of heme presence, while histidine modification in ApoHb points to a metal-catalyzed pathway.