Bromide - in Biology

In Biology

Bromide is needed by eosinophils (white blood cells of the granulocyte class, specialized for dealing with multi-cellular parasites), which use it to generate antiparasitic brominating compounds such as hypobromite, by the action of eosinophil peroxidase, a haloperoxidase enzyme which is able to use chloride, but preferentially uses bromide when available. Despite this use by the body, bromide is not known to be strictly necessary for animal life, as its functions may generally be replaced (though in some cases not as well) by chloride. Land plants also do not use bromide.

Bromide salts are also sometimes used in hot tubs and spas as mild germicidal agents, using the action of an added oxidizing agent to generate in situ hypobromite, in a similar fashion to the peroxidase in eosinophils.

Bromide is also not a necessary nutrient for most animals in the sea, although a few sea animals, such as Murex snails, use bromide to make organic compounds. However, bromide ion is heavily concentrated by some species of ocean algae, which construct methyl bromide and a great number of bromoorganic compounds with it, using the unusual enzymes called vanadium bromoperoxidases to do these reactions.

The average concentration of bromide in human blood is 5.3±1.4 mg/L and varies with age and gender. Much higher levels may indicate exposure to brominated chemicals (e.g. methyl bromide). However, since bromide occurs in relatively high concentration in seawater and many types of seafood, bromide concentrations in the blood are heavily influenced by seafood contributions to the diet.