Haloperoxidase

Haloperoxidases are

Halogenations of organic compounds by free halogens (F₂, Cl₂, Br₂, and sometimes I₂) is generally favorable process. It is practiced industrially on a large scale for example. In nature, however, free halogens do not exist in appreciable amounts. The combination of hydrogen peroxide, which is widely produced by aerobic life, and halide anionsCl⁻, Br⁻, I⁻ provides the equivalent of Cl₂, Br₂, I₂. The oxidation of these anions by hydrogen peroxide is slow in the absence of enzymes. These enzymes are called haloperoxidases. The reaction that they catalyze is:

X⁻ + H₂O₂ + H⁺ + R−H → X + 2 H₂O + R−X

From the perspective of thermodynamics, the

The classification of these enzymes by substrate-usability does not necessarily indicate enzyme substrate preference. For example, although eosinophil peroxidase is able to oxidize chloride, it preferentially oxidizes bromide.^[3]

The mammalian haloperoxidases

A specific vanadium bromoperoxidase in marine organisms (fungi, bacteria, microalgae, perhaps other eukaryotes) uses vanadate and hydrogen peroxide to brominate electrophilic organics.^[5]

• Vanadium bromoperoxidase

References