title: In vitro dehalogenation of tetrachloroethylene (PCE) by cell-free extracts of Clostridium bifermentans DPH-1.
abstract: Cell-free extracts of Clostridium bifermentans DPH-1 catalyzed tetrachloroethylene (PCE) dechlorination. PCE degradation was stimulated by addition of a variety of electron donors. Ethanol (0.61 mM) was the most effective electron donor for PCE dechlorination. Maximum activity was recorded at 30 degrees C and pH 7.5. Addition of NADH as a cofactor stimulated enzymatic activity but the activity was not stimulated by addition of metal ions. When the cell-free enzyme extract was incubated in the presence of titanium citrate as a reducing agent, the dehalogenase was rapidly inactivated by propyl iodide (0.5 mM). The activity of propyliodide-reacted enzyme was restored by illumination with a 250 W lamp. The dehalogenase activity was also inhibited by cyanide. The substrate spectrum of activity included trichloroethylene (TCE), cis-1,2-dichloroethylene (cDCE), trans-dichloroethylene, 1,1-dichloroethylene, 1,2-dichloroethane, and 1,1,2-trichloroethane. The highest rate of degradation of the chlorinated aliphatic compounds was achieved with PCE, and PCE was principally degraded via TCE to cDCE. Results indicate that the dehalogenase could play a vital role in the breakdown of PCE as well as a variety of other chlorinated aliphatic compounds.
authors.affiliation: Department of Bioprocessing, Faculty of Agriculture, Gifu University, Yanagido, Japan.
authors.forename: Y C
authors.initials: YC
authors.lastname: Chang
authors.forename: B C
authors.initials: BC
authors.lastname: Okeke
authors.forename: M
authors.initials: M
authors.lastname: Hatsu
authors.forename: K
authors.initials: K
authors.lastname: Takamizawa
mesh_terms: D001673:Biodegradation, Environmental / Q000187:drug effects; D019343:Citric Acid / Q000494:pharmacology; D003013:Clostridium / Q000378:metabolism*; D004579:Electron Transport; D004785:Environmental Pollutants / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000431:Ethanol / Q000378:metabolism; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011190:Potassium Cyanide / Q000494:pharmacology; D013750:Tetrachloroethylene / Q000378:metabolism*; D015262:Xenobiotics / Q000378:metabolism
chemical_list: D004785:Environmental Pollutants; D004791:Enzyme Inhibitors; D006843:Hydrocarbons, Chlorinated; D015262:Xenobiotics; C419387:titanium citrate; D019343:Citric Acid; D000431:Ethanol; D010088:Oxidoreductases; C112990:tetrachloroethene dehalogenase; D011190:Potassium Cyanide; D013750:Tetrachloroethylene