PROPERTIES OF TETRACHLOROETHENE AND TRICHLOROETHENE DEHALOGENASE OF DEHALOSPIRILLUM MULTIVORANS

Some properties of tetrachloroethene and trichloroethene dehalogenase of the recently isolated, tetrachloroethene-utilizing anaerobe, Dehalo spirillum multivorans, were studied with extracts of cells grown on py ruvate plus fumarate. The dehalogenase catalyzed the oxidation of redu ced methyl viologen with tetrachloroethene (PCE) or trichloroethene (T CE) as electron acceptor. All other artificial or physiological electr on donors tested were ineffective. The PCE and TCE dehalogenase activi ty was insensitive towards oxygen in crude extracts. When extracts wer e incubated under anoxic conditions in the presence of titanium citrat e as reducing agent, the dehalogenase was rapidly inactivated by propy l iodide (50 mu M). Inactivation did not occur in the absence of titan ium citrate. The activity of propyl-iodide-treated extracts was restor ed almost immediately by illumination The dehalogenase was inhibited b y cyanide. The inhibition profile was almost the same under oxic and a noxic conditions independent of the presence or absence of titanium ci trate. In addition, N2O, nitrite, and ethylene diamine tetra-acetate ( EDTA) were inhibitors of PCE and TCE dehalogenase. Carbon monoxide and azide had no influence on the dehalogenase activity. Trans-1,2-dichlo roethene or 1,1-dichloroethene, both of which are isomers of the dechl orination product cis-1,2-dichloroethene, neither inhibited nor inacti vated the dehalogenase. PCE and TCE dechlorination appeared to be medi ated by the same enzyme since the inhibitors tested had nearly the sam e effects on the PCE and TCE dehalogenating activity. The data indicat ed the involvement of a corrinoid and possibly of an additional transi tion metal in reductive PCE and TCE dechlorination.