Reaction: RH + chloride + H2O2 = RCl + 2 H2O
Other name(s): chloroperoxidase; CPO; vanadium haloperoxidase
Systematic name: chloride:hydrogen-peroxide oxidoreductase
Comments: Brings about the chlorination of a range of organic molecules, forming stable C-Cl bonds. Also oxidizes bromide and iodide. Enzymes of this type are either heme-thiolate proteins, or contain vanadate. A secreted enzyme produced by the ascomycetous fungus Caldariomyces fumago (Leptoxyphium fumago) is an example of the heme-thiolate type. It catalyses the production of hypochlorous acid by transferring one oxygen atom from H2O2 to chloride. At a separate site it catalyses the chlorination of activated aliphatic and aromatic substrates, via HClO and derived chlorine species. In the absence of halides, it shows peroxidase (e.g. phenol oxidation) and peroxygenase activities. The latter inserts oxygen from H2O2 into, for example, styrene (side chain epoxidation) and toluene (benzylic hydroxylation), however, these activities are less pronounced than its activity with halides. Has little activity with non-activated substrates such as aromatic rings, ethers or saturated alkanes. The chlorinating peroxidase produced by ascomycetous fungi (e.g. Curvularia inaequalis) is an example of a vanadium chloroperoxidase, and is related to bromide peroxidase (EC 184.108.40.206). It contains vanadate and oxidizes chloride, bromide and iodide into hypohalous acids. In the absence of halides, it peroxygenates organic sulfides and oxidizes ABTS [2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid)] but no phenols.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9055-20-3
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