Reaction: Cl– + H2O2 + H+ = HClO + H2O
Other name(s): MPO; verdoperoxidase
Systematic name: chloride:hydrogen-peroxide oxidoreductase (hypochlorite-forming)
Comments: Contains calcium and covalently bound heme (proximal ligand histidine). It is present in phagosomes of neutrophils and monocytes, where the hypochlorite produced is strongly bactericidal. It differs from EC 1.11.1.10 chloride peroxidase in its preference for formation of hypochlorite over the chlorination of organic substrates under physiological conditions (pH 5-8). Hypochlorite in turn forms a number of antimicrobial products (Cl2, chloramines, hydroxyl radical, singlet oxygen). MPO also oxidizes bromide, iodide and thiocyanate. In the absence of halides, it oxidizes phenols and has a moderate peroxygenase activity toward styrene.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:
References:
1. Agner, K. Myeloperoxidase. Advances in Enzymology 3 (1943) 137-148.
2. Harrison, J.E. and Schultz, J. Studies on the chlorinating activity of myeloperoxidase. J. Biol. Chem. 251 (1976) 1371-1374. [PMID: 176150]
3. Furtmuller, P.G., Burner, U. and Obinger, C. Reaction of myeloperoxidase compound I with chloride, bromide, iodide, and thiocyanate. Biochemistry 37 (1998) 17923-17930. [PMID: 9922160]
4. Tuynman, A., Spelberg, J.L., Kooter, I.M., Schoemaker, H.E. and Wever, R. Enantioselective epoxidation and carbon-carbon bond cleavage catalyzed by Coprinus cinereus peroxidase and myeloperoxidase. J. Biol. Chem. 275 (2000) 3025-3030. [PMID: 10652281]
5. Klebanoff, S.J. Myeloperoxidase: friend and foe. J Leukoc Biol 77 (2005) 598-625. [PMID: 15689384]
6. Fiedler, T.J., Davey, C.A. and Fenna, R.E. X-ray crystal structure and characterization of halide-binding sites of human myeloperoxidase at 1.8 Å resolution. J. Biol. Chem. 275 (2000) 11964-11971. [PMID: 10766826]
7. Gaut, J.P., Yeh, G.C., Tran, H.D., Byun, J., Henderson, J.P., Richter, G.M., Brennan, M.L., Lusis, A.J., Belaaouaj, A., Hotchkiss, R.S. and Heinecke, J.W. Neutrophils employ the myeloperoxidase system to generate antimicrobial brominating and chlorinating oxidants during sepsis. Proc. Natl. Acad. Sci. USA 98 (2001) 11961-11966. [PMID: 11593004]