Dichloromethane dehalogenase of Hyphomicrobium sp. strain DM2

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Abstract
Dichloromethane dehalogenase, a highly inducible glutathione-dependent enzyme catalyzing the conversion of dichloromethane into formaldehyde and inorganic chloride, was purified 5-fold with 60% yield from Hyphomicrobium sp. strain DM2. The electrophoretically homogeneous purified enzyme exhibited a specific activity of 17.3 mkat/kg of protein. Its pH optimum was 8.5. The enzyme was stable at -20.degree. C for at least 6 mo. A subunit MW of 33,000 was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Gel filtration of native dichloromethane dehalogenase yielded a MW of 195,000. Subunit cross-linking with dimethyl suberimidate confirmed the hexameric tertiary structure of the enzyme. Dichloromethane dehalogenase was highly specific for dihalomethanes. Its apparent Km values were 30 .mu.M for CH2Cl2, 15 .mu.M for CH2BrCl, 13 .mu.M for CH2Br2, 5 .mu.M for CH2I2 and 320 .mu.M for glutathione. Several chlorinated aliphatic compounds inhibited the dichloromethane dehalogenase activity of pure enzyme. The Ki values of the competitive inhibitors 1,2-dichloroethane and 1-chloropropane were 3 and 56 .mu.M, respectively.