Purification and characterization of a bacterial dehalogenase with activity toward halogenated alkanes, alcohols and ethers

Abstract

An enzyme that is capable of hydrolytic conversion of halogenated aliphatic hydrocarbons to their corresponding alcohols was purified from a 1,6‐dichlorohexane‐degrading bacterium. The dehalogenase was found to be a monomeric protein of relative molecular mass 28000. The affinity for its substrates was relatively low with Km values for short‐chain haloalkanes in the range 0.1–0.9 mM. The aliphatic dehalogenase showed a much broader substrate range than has been reported for halidohydrolases so far. Novel classes of substrates include dihalomethanes, C5–C9 1 ‐halo‐n‐alkanes, secondary alkylhalides, halogenated alcohols and chlorinated ethers. Several of these compounds are important environmental pollutants, e.g. methylbromide, dibromomethane, 1,2‐dibromoethane, 1,3‐dichloropropene, and bis(2‐chloroethyl)ether. The degradation of chiral 2‐bromoalkanes appeared to proceed without stereochemical preference. Optically active 2‐bromobutane was converted with inversion of configuration at the chiral carbon atom, suggesting that the dehalogenase reaction proceeds by a nucleophilic substitution involving a carboxyl group or base catalysis. Copyright © 1988, Wiley Blackwell. All rights reserved