Vanadium bromoperoxidase

Vanadium bromoperoxidases have been found in bacteria, fungi, marine macro algae (seaweeds), and marine microalgae (diatoms) which produce brominated organic compounds.^[2] It has not been definitively identified as the bromoperoxidase of higher eukaryotes, such as murex snails, which have a very stable and specific bromoperoxidase, but perhaps not a vanadium dependent one.^[3] While the purpose of the bromoperoxidase is still unknown, the leading theories include that it’s a way of regulating hydrogen peroxide produced by photosynthesis and/or as a self-defense mechanism by producing hypobromous acid which prevents the growth of bacteria.^[4][5]

The enzymes catalyse the oxidation of bromide (0.0067% of sea water) by hydrogen peroxide. The resulting electrophilic bromonium cation (Br⁺) attacks hydrocarbons (symbolized as R-H in the following equation):

R-H + Br⁻ + H₂O₂ → R-Br + H₂O + OH⁻

The bromination acts on a variety of dissolved organic matter and increasingly bromination leads to the formation of bromoform.^[6] The vanadium bromoperoxidases produce an estimated 1–2 million tons of bromoform and 56,000 tons of bromomethane annually.^[7] Partially in the polar regions, which has high blooms of microalgae in the spring, these compounds have the potential to enter the troposphere and lower stratosphere.^[8][9] Through photolysis, brominated methanes produce a bromine radical (Br^.) that can lead to ozone depletion.^[10] Most of the earth's natural organobromine compounds arise by the action of this enzyme.

• "active site". Jmol (chemapps.stolaf.edu). Interactive image. Northfield, MN: St. Olaf College.
• Example structure: 1qhb
• Family/Domain classifications:
  • "Family a.111.1.2". SCOP. Haloperoxidase (bromoperoxidase). U.C. Berkeley, Berkeley, California.
  • "Superfamily 1.10.606.10". CATH database. Vanadium-containing chloroperoxidase, domain 2.
  • "cd03398 PAP2 haloperoxidase". CDD (ncbi.nlm.nih.gov). Bethesda, MD: U.S. National Institutes of Health.
  • "whole protein". InterPro. Hinxton, Cambridgeshire, UK: European Bioinformatics Institute.

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