Ceruloplasmin Is an Endogenous Inhibitor of Myeloperoxidase

• Published in: The Journal of biological chemistry Vol. 288; no. 9; pp. 6465 - 6477
• Main Authors: Chapman, AnnaL.P., Mocatta, TessaJ, Shiva, Sruti, Seidel, Antonia, Chen, Brian, Khalilova, Irada, Paumann-Page, Martina E., Jameson, GuyN.L., Winterbourn, ChristineC, Kettle, Anthony J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.2013; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Ascorbic Acid - blood; Ceruloplasmin; Ceruloplasmin - chemistry; Ceruloplasmin - genetics; Ceruloplasmin - isolation & purification; Ceruloplasmin - metabolism; Enzyme Inhibitors; Enzyme Inhibitors - blood; Enzyme Inhibitors - chemistry; Enzyme Inhibitors - isolation & purification; Enzymology; Humans; Hypochlorous Acid - blood; Inflammation; Inflammation - blood; Mice; Mice, Knockout; Myeloperoxidase; Neutrophil; Oxidation-Reduction; Oxidative Stress; Peroxidase - antagonists & inhibitors; Peroxidase - blood; Peroxidase - chemistry; Peroxidase - genetics; Peroxidase - isolation & purification; Protein Binding; Reactive Oxygen Species (ROS); Ceruloplasmin; Enzyme Inhibitors; Reactive Oxygen Species (ROS); Oxidative Stress; Myeloperoxidase; Inflammation; Neutrophil
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.418970

Myeloperoxidase is a neutrophil enzyme that promotes oxidative stress in numerous inflammatory pathologies. It uses hydrogen peroxide to catalyze the production of strong oxidants including chlorine bleach and free radicals. A physiological defense against the inappropriate action of this enzyme has yet to be identified. We found that myeloperoxidase oxidized 75% of the ascorbate in plasma from ceruloplasmin knock-out mice, but there was no significant loss in plasma from wild type animals. When myeloperoxidase was added to human plasma it became bound to other proteins and was reversibly inhibited. Ceruloplasmin was the predominant protein associated with myeloperoxidase. When the purified proteins were mixed, they became strongly but reversibly associated. Ceruloplasmin was a potent inhibitor of purified myeloperoxidase, inhibiting production of hypochlorous acid by 50% at 25 nm. Ceruloplasmin rapidly reduced Compound I, the FeV redox intermediate of myeloperoxidase, to Compound II, which has FeIV in its heme prosthetic groups. It also prevented the fast reduction of Compound II by tyrosine. In the presence of chloride and hydrogen peroxide, ceruloplasmin converted myeloperoxidase to Compound II and slowed its conversion back to the ferric enzyme. Collectively, our results indicate that ceruloplasmin inhibits myeloperoxidase by reducing Compound I and then trapping the enzyme as inactive Compound II. We propose that ceruloplasmin should provide a protective shield against inadvertent oxidant production by myeloperoxidase during inflammation. Background: Myeloperoxidase promotes oxidative stress during inflammation by producing hypochlorous acid. Results: Ceruloplasmin was a potent inhibitor of myeloperoxidase and slowed its activity in plasma from wild type mice compared with ceruloplasmin knock-out animals. Conclusion: Ceruloplasmin is a physiologically relevant inhibitor of myeloperoxidase. Significance: Ceruloplasmin will provide a protective shield against oxidant production by myeloperoxidase during inflammation.