enzymology Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

, a haloacetate dehalogenase () is an enzyme that

catalyzes Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

the chemical reaction :haloacetate + H₂O

\rightleftharpoons

glycolate + halide Thus, the two substrates of this enzyme are haloacetate and H₂O, whereas its two products are glycolate and

halide In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...

. For examples, in the case of fluoroacetate in will produce glycolate and

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typ ...

. This enzyme belongs to the family of hydrolases, one of the largest known enzyme families comprising approximately 1% of the genes in the human genome, exists as a homodimer, and acts specifically halide bonds in carbon-halide compounds. The systematic name of this enzyme class is haloacetate halidohydrolase. This enzyme is also called monohaloacetate dehalogenase and fluoroacetate dehalogenase. This enzyme participates in

gamma-hexachlorocyclohexane degradation Lindane, also known as ''gamma''-hexachlorocyclohexane (γ-HCH), gammaxene, Gammallin and benzene hexachloride (BHC), is an organochlorine chemical and an isomer of hexachlorocyclohexane that has been used both as an agricultural insecticide and ...

and

1,2-dichloroethane degradation Onekama ( ) is a village in Manistee County in the U.S. state of Michigan. The population was 411 at the 2010 census. The village is located on the shores of Portage Lake and is surrounded by Onekama Township. The town's name is derived from "On ...

Reactions

Haloacetate dehalogenase is unique because it catalyzes the cleavage of the remarkably stable carbon–fluorine bond of a

fluorinated In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a chemical compound, compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the prod ...

aliphatic compound In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane, or ...

. 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 Water () is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, which is nearly colorless apart from an inherent hint of blue. It is by far the most studied chemical compound and is described as the "uni ...

directly attacks the substrate, displacing the

halogen The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...

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.

Structural studies

As of late 2007, only one

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

has been solved for this class of enzymes, with the PDB accession code .

References

* * * The Japan Chemical Journal Forum and Wiley Periodicals, Inc.2008 * MacKenzie, D. Trouble in the wind over altered soya beans. New Scientist. Vol 148 (2006),pp12. December 2, 1995 * 1995 Soy Stats. American Soybean Association Homepage. * Plant biotech will hit farming sector radar screen in 1996. BioBusiness. December 8, 1995 * Tatsuo Kurihara Journal of Biochemistry. Vol. 131, pp. 671–677 (2002), Regular paper;2002 EC 3.8.1 Enzymes of known structure {{hydrolase-stub