INITIAL CHARACTERIZATION OF A REDUCTIVE DEHALOGENASE FROM DESULFITOBACTERIUM CHLORORESPIRANS CO23

Desulfitobacterium chlororespirans Co23 is capable of using 3-chloro-4 -hydroxybenzoate as terminal electron acceptor for growth. Membrane pr eparations from cells grown fermentatively on pyruvate in the presence of 3-chloro-4-hydroxybenzoate dechlorinated this compound at a rate o f 3.9 nmol min(-1) mg of protein(-1). Fivefold-greater dechlorination rates were measured with reduced methyl viologen as the artificial ele ctron donor. Reduced benzyl viologen, NADH, NADPH, reduced flavin aden ine dinucleotide, and reduced flavin mononucleotide could not substitu te for reduced methyl viologen. The maximal initial rate of catalysis was achieved at pH 6.5 and 60 degrees C. The membrane-bound dechlorina ting enzyme system was not oxygen sensitive and was stable at 57 degre es C for at least 2 h. Sulfite inhibited dechlorination in cell-free a ssays, whereas sulfate did not. Several chlorophenols were dehalogenat ed exclusively in the ortho position by cell extracts.