title: Enzymatic dehalogenation of gas phase substrates with haloalkane dehalogenase.
abstract: Haloalkane dehalogenase is an enzyme capable of catalyzing the conversion of short-chained (C(2)-C(8)) aliphatic halogenated hydrocarbons to a corresponding primary alcohol. Because of its broad substrate specificity for mono-, di-, and trisubstituted halogenated hydrocarbons and cofactor independence, haloalkane dehalogenases are attractive biocatalysts for gas-phase bioremediation of pollutant halogenated vapor emissions. A solid preparation of haloalkane dehalogenase from Rhodococcus rhodochrous was used to catalyze the dehalogenation reaction of 1-chlorobutane or 1,3-dichloropropane delivered in the gas phase. For optimal gas-phase dehalogenase activity, a relative humidity of 100%, a(w) = 1, was desired. With a 50% reduction in the vapor-phase hydration level, an 80% decrease in enzymatic activity was observed. The enzyme kinetics for the gas-phase substrates obeyed an Arrhenius-"like" behavior and the solid haloalkane dehalogenase preparation was more thermally stable than its water-soluble equivalent. Triethylamine was added to the gaseous reaction environment in efforts to increase the rate of reaction. A tenfold increase in the dehalogenase activity for the vapor-phase substrates was observed with the addition of triethylamine. Triethylamine altered the electrostatic environment of haloalkane dehalogenase via a basic shift in local pH, thereby minimizing the effect of the pH-reducing reaction product on enzyme activity. Both organic phase and solid-state buffers were used to confirm the activating role of the altered ionization state.
authors.affiliation: Department of Chemical and Petroleum Engineering, University of Pittsburgh, PA 15261, USA.
authors.forename: B C
authors.initials: BC
authors.lastname: Dravis
authors.forename: K E
authors.initials: KE
authors.lastname: LeJeune
authors.forename: A D
authors.initials: AD
authors.lastname: Hetro
authors.forename: A J
authors.initials: AJ
authors.lastname: Russell
mesh_terms: D000393:Air Pollutants / Q000737:chemistry / Q000378:metabolism; D001673:Biodegradation, Environmental; D002021:Buffers; D002073:Butanes / Q000378:metabolism; D002384:Catalysis / Q000187:drug effects; D002849:Chromatography, Gas / Q000379:methods; D005021:Ethylamines / Q000494:pharmacology; D006219:Halogens / Q000378:metabolism*; D006846:Hydrocarbons, Halogenated / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006867:Hydrolases / Q000378:metabolism*; D007700:Kinetics; D011407:Propane / Q000031:analogs & derivatives / Q000378:metabolism; D012240:Rhodococcus / Q000201:enzymology*; D012995:Solubility; D055672:Static Electricity; D013696:Temperature; D014867:Water / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D002021:Buffers; D002073:Butanes; D005021:Ethylamines; D006219:Halogens; D006846:Hydrocarbons, Halogenated; D014867:Water; C067434:1,3-dichloropropane; D006867:Hydrolases; C046137:haloalkane dehalogenase; D011407:Propane; C016162:triethylamine; C006854:butyl chloride