Chloride peroxidase explained

Chloride peroxidase
Ec Number:	1.11.1.10
Cas Number:	9055-20-3

Chloride peroxidase is a family of enzymes that catalyzes the chlorination of organic compounds. This enzyme combines the inorganic substrates chloride and hydrogen peroxide to produce the equivalent of Cl⁺, which replaces a proton in hydrocarbon substrate:

R-H + Cl⁻ + H₂O₂ + H⁺ → R-Cl + 2 H₂OIn fact the source of "Cl⁺" is hypochlorous acid (HOCl).^[1] Many organochlorine compounds are biosynthesized in this way.

This enzyme belongs to the family of oxidoreductases, specifically those acting on a peroxide as acceptors (peroxidases). The systematic name of this enzyme class is chloride:hydrogen-peroxide oxidoreductase. This enzyme is also called chloroperoxidase. It employs one cofactor which may be either heme or vanadium.^[2]

The heme-containing chloroperoxidase (CPO) exhibits peroxidase, catalase and cytochrome P450-like activities in addition to catalyzing halogenation reactions.^[3] Despite functional similarities with other heme enzymes, the structure of CPO is unique, which folds into a tertiary structure dominated by eight helical segments. The catalytic acid base, required to cleave the peroxide O-O bond, is glutamic acid rather than histidine as in horseradish peroxidase.

Structural studies

As of late 2007, 30 structures have been solved for this class of enzymes, with PDB accession codes,,,,,,,,,,,,,,,,,,,,,,,,,,,,, and .

Further reading

• Hager LP, Hollenberg PF, Rand-Meir T, Chiang R, Doubek D . 1975 . Chemistry of peroxidase intermediates . Ann. N. Y. Acad. Sci. . 244 . 1 . 80 - 93 . 1056179 . 10.1111/j.1749-6632.1975.tb41524.x . 1975NYASA.244...80H . 27336177 .
• Morris DR, Hager LP . 1966 . Chloroperoxidase. I. Isolation and properties of the crystalline glycoprotein . J. Biol. Chem. . 241 . 1763 - 8 . 5949836 . 8 .
• Theiler R, Cook JC, Hager LP, Siuda JF . 1978 . Halohydrocarbon synthesis by homoperoxidase . Science . 202 . 1094 - 1096 . 10.1126/science.202.4372.1094 . 17777960 . 4372 . 1978Sci...202.1094T . 21448823 .

Notes and References

1. Hofrichter. M.. Ullrich. R.. Pecyna. Marek J.. Christiane . Liers. Taina . Lundell. Appl Microbiol Biotechnol. 2010. 87. 10.1007/s00253-010-2633-0. 871–897 . New and classic families of secreted fungal heme peroxidases. 3. 20495915. 24417282.
2. Natural Product Reports. 2004. 21. 1. 15039842. 10.1039/b302337k. The role of vanadium bromoperoxidase in the biosynthesis of halogenated marine natural products. Alison. Butler. Carter-Franklin, Jayme N.. 180–8. (this paper also discussed chloroperoxidases.
3. 10.1016/S0969-2126(01)00274-X . Poulos TL, Sundaramoorthy M, Terner J . The crystal structure of chloroperoxidase: a heme peroxidase--cytochrome P450 functional hybrid . Structure . 3 . 12 . 1367–1377 . 1995 . 8747463. free .