Description

Haloperoxidases catalyze the oxidative transformation of halides (Cl₂, Br₂ or I₂) to XO- (X can be Cl, Br or I), or organic halogen compounds in the presence of hydrogen peroxide. Haloperoxidases catalyze the oxidation of halides, and they are named according to the most electronegative halide that they can oxidize; chloroperoxidases can catalyze the oxidation of chloride, as well as of bromide and iodide, bromoperoxidases react with bromide and iodide, whereas iodoperoxidases are specific of iodide.
The ability of haloperoxidases to halogenate a broad range of organic compounds of both commercial and pharmaceutical interest, as well as their high stability toward high temperatures, oxidative conditions, and in the presence of organic solvents, makes them good candidates for use in industrial biotransformations.

Tree classes of haloperoxidases have detected based on the presence or abscence of haem (replaced or no by metal). The amino acid sequence identities between the different Haloperoxidase classes are low.

HalPrx: HalPrx are hemeproteins which contain contain protoporphyrin IX as a prosthetic group. HalPrx is also called chloroperoxidase (CPO). This versatile heme-containing enzyme that exhibits peroxidase, catalase and cytochrome P450-like activities in addition to catalyzing halogenation reactions. HalPrx acts on Cl^-, Br^-, and I^-. Despite functional similarities with other heme enzymes, HalPrx folds into a novel tertiary structure dominated by eight helical segments. The catalytic base, required to cleave the peroxide O-O bond, is glutamic acid rather than histidine as in other peroxidases. They are only found in fungi (Ascomycetes and Basidiomycetes) with the exception of 3 sequences coming from Phytophthora. Catalyzes peroxidative halogenations involved in the biosynthesis of clardariomycin (2,2-dichloro-1,3-cyclo- pentenedione). The enzyme also has potent catalase activity and in the absence of halide ion, acts as a peroxidase similar to plant peroxidases.

HalVPrx: Some haloperoxidase are non-haem and contain vanadium instead of haem. HalVPrx require vanadium in the form of vanadate as cofactor for the enzyme activity. HalVPrx can be chloroperoxidase (vCPO), bromoperoxidase (vBPO) and iodoperoxidase (vIPO). HalVPrx are detected in brown and red algae, in bacteria, in cyanobacteria and in some ascomycetes.

HalNPrx: HalNPrx are non haem, chloroperoxidases enzymes. They are only found in procakyotes (bacteria)