GENETICS AND BIOCHEMISTRY OF DEHALOGENATING ENZYMES

Microorganisms that can utilize halogenated compounds as a growth subs trate generally produce enzymes whose function is carbon-halogen bond cleavage. Based on substrate range, reaction type and gene sequences, the dehalogenating enzymes can be classified in different groups, incl uding hydrolytic dehalogenases, glutathione transferases, monooxygenas es and hydratases. X-ray crystallographic and biochemical studies have provided detailed mechanistic insight into the action of haloalkane d ehalogenase. The essential features are nucleophilic substitution of t he halogen by a carboxylate group and the presence of a distinct halog en binding site, formed by tryptophan residues. This review summaries current knowledge on a variety of other dehalogenating enzymes and ind icates the existence of a widespread and diverse microbial potential f or dechlorination of natural and xenobiotic halogenated compounds.