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Oxidative modification of ovalbumin
S Olszowski1, E Olszowska, T Stelmaszyńska
1Jagiellonian University, Collegium Medicum, Institute of Medical Biochemistry, Cracow, Poland.
Acta Biochimica Polonica
|January 1, 1996
Summary
Neutrophil-derived reactive oxygen species modify ovalbumin (OVA). Chlorination by hypochlorous acid (HOCl) and subsequent oxidation by hydrogen peroxide (H2O2) alter protein structure and promote aggregation.
Area of Science:
- Biochemistry
- Protein Chemistry
- Oxidative Stress
Background:
- Stimulated neutrophils produce reactive oxygen species (ROS) like hypochlorous acid (HOCl) and hydrogen peroxide (H2O2).
- These ROS can modify proteins, leading to altered function and potential aggregation.
- Ovalbumin (OVA) serves as a model protein to study these oxidative modifications.
Purpose of the Study:
- To investigate the sequential modification of OVA by HOCl and H2O2.
- To monitor changes in functional groups and their accessibility.
- To understand the role of these modifications in protein aggregation.
Main Methods:
- Sequential treatment of OVA with HOCl and H2O2.
- Analysis of functional group modifications (amino, sulfhydryl, disulfide, carbonyl, tyrosine, tryptophan).
- Assessment of protein aggregation using SDS/PAGE and HPLC.
Main Results:
- Chlorination by HOCl led to disulfide bond formation and decreased sulfhydryl content.
- Amino groups were oxidized to carbonyls, shifting the isoelectric point (pI) acidic.
- Tryptophan was the initial chlorination target, with chlorotyrosine forming and subsequently transforming to bityrosine upon H2O2 treatment.
- HOCl chlorination induced aggregation stabilized by non-covalent bonds.
Conclusions:
- Sequential oxidation by HOCl and H2O2 significantly alters OVA structure.
- Protein aggregation is promoted by HOCl-induced modifications.
- A molar excess of approximately 2 HOCl per reactive group in OVA initiates substantial structural changes.