Microbial Dehalogenation of Synthetic Organohalogen Compounds: Hydrolytic Dehalogenases

Hydrolytic removal of halogen substitutents is commonly the first step in the degradation of haloaliphatic compounds by aerobic bacteria, whereas initial dehalogenation of aryl halides is rare. Hydrolytic dehalogenations are catalyzed by specific dehalogenases, a group of enzymes which has been extensively studied in bacteria and which does not seem to occur in mammals. Questions pertaining to the origin and evolution of dehalogenases in soil bacteria have recently become tractable by the establishment of dehalogenase gene sequences. At the protein level, new dehalogenases are being discovered and known dehalogenases are being analyzed with respect to their mechanisms of catalysis. Finally, microbial dehalogenases, either as cells of dehalogenative bacteria or as enzyme preparations, have potential for applications in environmental biotechnology and biotransformation.