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Peroxynitrite releases copper from caeruloplasmin: implications for atherosclerosis
J A Swain1, V Darley-Usmar, J M Gutteridge
1Department of Anaesthesia and Intensive Care, Royal Brompton Hospital National Heart & Lung Institute, London, UK.
FEBS Letters
|March 28, 1994
Summary
Peroxynitrite damages caeruloplasmin, a key protein in blood vessels, by releasing its copper. This process creates a new ferroxidase activity linked to oxidized lipids.
Area of Science:
- Biochemistry
- Vascular Biology
- Oxidative Stress
Background:
- Peroxynitrite, formed from superoxide and nitric oxide in the vasculature, is a potent oxidant.
- Caeruloplasmin is a blue, copper-containing protein with ferroxidase activity, crucial for iron metabolism and antioxidant defense.
- Oxidative stress and the role of caeruloplasmin in vascular health are areas of significant research interest.
Purpose of the Study:
- To investigate the effects of peroxynitrite on caeruloplasmin in vitro and in plasma.
- To characterize the changes in caeruloplasmin's activity and structure upon exposure to peroxynitrite.
- To identify any novel ferroxidase activities that emerge following peroxynitrite-induced damage.
Main Methods:
- Incubation of purified caeruloplasmin with peroxynitrite.
- Incubation of normal human plasma with peroxynitrite.
- Assay of ferroxidase activity before and after incubation.
- Spectrophotometric analysis to monitor color loss and copper release.
Main Results:
- Peroxynitrite treatment released copper from purified caeruloplasmin, leading to loss of its blue color and ferroxidase activity.
- In normal plasma, peroxynitrite also released copper from caeruloplasmin, despite reacting with other plasma components.
- A secondary azide-insensitive ferroxidase activity, associated with peroxidized lipids, was detected in plasma after peroxynitrite exposure.
Conclusions:
- Peroxynitrite effectively inactivates caeruloplasmin by copper release, impacting its ferroxidase function.
- The formation of a novel, lipid-associated ferroxidase activity suggests a compensatory or alternative mechanism in response to oxidative damage.
- These findings highlight the detrimental effects of peroxynitrite on critical vascular proteins and indicate potential alterations in enzymatic activity during oxidative stress.