Chloride peroxidase

Chloride peroxidase (EC 1.11.1.10) 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 H₂O

In fact the source of "Cl⁺" is hypochlorous acid (HOCl). 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.

The heme-containing chloroperoxidase (CPO) exhibits peroxidase, catalase and cytochrome P450-like activities in addition to catalyzing halogenation reactions. 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 PDB: 1A7U​, PDB: 1A88​, PDB: 1A8Q​, PDB: 1A8S​, PDB: 1A8U​, PDB: 1BRT​, PDB: 1CPO​, PDB: 1IDQ​, PDB: 1IDU​, PDB: 1QHB​, PDB: 1QI9​, PDB: 1VNC​, PDB: 1VNE​, PDB: 1VNF​, PDB: 1VNG​, PDB: 1VNH​, PDB: 1VNI​, PDB: 1VNS​, PDB: 2CIV​, PDB: 2CIW​, PDB: 2CIX​, PDB: 2CIY​, PDB: 2CIZ​, PDB: 2CJ0​, PDB: 2CJ1​, PDB: 2CJ2​, PDB: 2CPO​, PDB: 2J18​, PDB: 2J19​, and PDB: 2J5M​.

References

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. Bibcode:1975NYASA.244...80H. doi:10.1111/j.1749-6632.1975.tb41524.x. PMID 1056179. S2CID 27336177.
• Morris DR, Hager LP (1966). "Chloroperoxidase. I. Isolation and properties of the crystalline glycoprotein". J. Biol. Chem. 241 (8): 1763–8. doi:10.1016/S0021-9258(18)96701-3. PMID 5949836.
• Theiler R, Cook JC, Hager LP, Siuda JF (1978). "Halohydrocarbon synthesis by homoperoxidase". Science. 202 (4372): 1094–1096. Bibcode:1978Sci...202.1094T. doi:10.1126/science.202.4372.1094. PMID 17777960. S2CID 21448823.