Fluoroacetate dehalogenase

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Fluoroacetate dehalogenase catalyzes the hydrolytic defluorination of the toxic fluoroacetate to produce glycolate. This enzyme is unique in that it catalyzes the cleavage of a strong carbon–fluorine bond of an aliphatic compound. The enzyme also acts on chloroacetate, although much less efficiently.

The enzyme belongs to the hydrolase superfamily (one of the largest known enzyme families comprising approximately 1% of the genes in the human genome) and exists as a homodimer.

Reactions

Fluoroacetate dehalogenase is unique because it catalyzes the cleavage of the remarkably stable carbon–fluorine bond of a fluorinated aliphatic compound. In the reaction of L-2-haloacid dehalogenase and fluoroacetate dehalogenase, the carboxylate group performs a nucleophilic attack on the alpha-carbon atom, moving the halogen atom. This action is common to haloalkane dehalogenase and 4-chlorobenzoyl-CoA dehalogenase. DL-2-Haloacid dehalogenase is unique in that a water molecule directly attacks the substrate, displacing the halogen atom.

Significance

As fluoroacetate is poisonous and present in plants endemic to Australia, Africa, and Central America, livestock are often killed by fluoroacetate poisoning. Fluoroacetate is lethal to sheep and cattle at doses of 0.25 to 0.5 mg/kg of body weight, and is a problem in the livestock industry. A fluoroacetate dehalogenase gene from the soil bacterium Moraxella species strain B was transferred into the rumen bacterium Butyrivibrio fibrisolvens and expressed in vitro at sufficiently high levels to detoxify fluoroacetate in the surrounding medium. Scientists and farmers want to determine a way to get B. fibrisolvens into either the animals or plants.

References

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  5. Tatsuo Kurihara Journal of Biochemistry. Vol. 131, pp. 671-677 (2002), Regular paper;2002
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