Characterization of 1-chlorohexane halidohydrolase, a dehalogenase of wide substrate range from an Arthrobacter sp

Abstract

1-Chlorohexane halidohydrolase from Arthrobacter sp. strain HA1 was purified to homogeneity by fractional precipitation, ion-exchange chromatography, gel filtration, and high-performance liquid chromatography gel filtration. The enzyme was a monomer with a molecular weight of about 37,000; its amino acid composition and N-terminal sequence were determined. The enzyme had a broad optimum around pH 9.5, a temperature optimum near 50 degrees C, an activation energy of 40 kJ/mol, and a molecular activity of 0.9 kat/mol. The substrate range of the enzyme included at least 50 halogenated compounds. 1-Chloroalkanes (C3 to C10), 1-bromoalkanes (C1 to C9), and 1-iodoalkanes (C1 to C7), but no 1-fluoroalkane, were substrates. Subterminally substituted, branched-chain, and nonsaturated haloalkanes were dehalogenated. Some halogenated aromatic substrates, e.g., bromobenzene and benzyl bromide, were hydrolyzed. Several alpha,omega-dihaloalkanes were subject to double dehalogenation. Thus, 1,2-dibromoethane was hydrolyzed first to 2-bromoethanol and then to 1,2-dihydroxyethane. Crude extracts of strain HA1 were found to contain a debrominase that cleaved bromoalkanes with long alkyl chains.