Oxidative Aggregation of Ceruloplasmin Induced by Hydrogen Peroxide is Prevented by Pyruvate

Abstract

Ceruloplasmin (CP) is a blue copper glycoprotein with multiple physiological functions including ferroxidase and oxidase activities. CP is also an important serum oxygen free radical (OFR) scavenger and antioxidant, exerting cardioprotective and antifibrillatory actions. Although it has been reported that CP activities can be inhibited by OFR, the intimate mechanism of this inactivation is still not clear. Exposure of bovine CP to H²O² induced inactivation of the protein as well as structural alterations as indicated by loss of protein bands by SDS-PAGE. Both phenomena were H²O² concentration and time dependent. HPLC gel filtration and capillary electrophoresis analysis of CP treated with H²O² revealed an aggregation of the protein. Quantification of dityrosine formation by fluorescence indicated the involvement of dityrosine bridging, which could be responsible for aggregation of CP under oxidative attack. Oxidative damage to CP under H²O² treatment was completely prevented by pyruvate, suggesting that the association of CP with antioxidants could extend the range of the protective action of this protein.

• Ceruloplasmin
• Hydrogen peroxide
• Metal-catalysed oxidation
• Aggregation
• Dityrosine bridges
• Pyruvate
• AE: aminoethyl
• AU: absorbance unit
• CP: ceruloplasmin
• CE: capillary electrophoresis
• DPD: N,N-diethyl-p-phenylenediamine
• EDTA: ethylenediamine tetraacetic acid
• HPLC: high performance liquid chromatography
• OFR: oxygen free radicals
• PDA: -phenylenediamine
• RFU: relative fluorescence unit
• SDS-PAGE: sodium dodecylsulfate-polyacrylamide gel electrophoresis