title: Methyl-coenzyme M reductase of Methanobacterium thermoautotrophicum delta H catalyzes the reductive dechlorination of 1,2-dichloroethane to ethylene and chloroethane.
abstract: Reductive dechlorination of 1,2-dichloroethane (1,2-DCA) to ethylene and chloroethane (CA) by crude cell extracts of Methanobacterium thermoautotrophicum delta H with H2 as the electron donor was stimulated by Mg-ATP. The heterodisulfide of coenzyme M (CoM) and 7-mercaptoheptanoylthreonine phosphate together with Mg-ATP partially inhibited ethylene production but stimulated CA production compared Mg-ATP alone. The pH optimum for the dechlorination was 6.8 (at 60 degrees C). Michaelis-Menten kinetics for initial product formation rates with different 1,2-DCA concentrations indicated the enzymatic character of the dechlorination. Apparent Kms for 1,2-DCA of 89 and 119 microM and Vmaxs of 34 and 20 pmol/min/mg of protein were estimated for ethylene and CA production, respectively. 3-Bromopropanesulfonate, a specific inhibitor for methyl-CoM reductase, completely inhibited dechlorination of 1,2-DCA. Purified methyl-CoM reductase, together with flavin adenine dinucleotide and a crude component A fraction which reduced the nickel of factor F430 in methyl-CoM reductase, converted 1,2-DCA to ethylene and CA with H2 as the electron donor. In this system, methyl-CoM reductase was also able to transform its own inhibitor 2-bromoethanesulfonate to ethylene.
authors.affiliation: Department of Microbiology, Wageningen Agricultural University, The Netherlands.
authors.forename: C
authors.initials: C
authors.lastname: Holliger
authors.forename: S W
authors.initials: SW
authors.lastname: Kengen
authors.forename: G
authors.initials: G
authors.lastname: Schraa
authors.forename: A J
authors.initials: AJ
authors.lastname: Stams
authors.forename: A J
authors.initials: AJ
authors.lastname: Zehnder
mesh_terms: D005018:Ethyl Chloride / Q000032:analysis / Q000378:metabolism*; D005025:Ethylene Dichlorides / Q000378:metabolism*; D005030:Ethylenes / Q000032:analysis / Q000378:metabolism*; D007700:Kinetics; D017014:Methanobacterium / Q000201:enzymology* / Q000254:growth & development; D008780:Methyltransferases / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000302:isolation & purification / Q000378:metabolism*; D014805:Vitamin B 12 / Q000494:pharmacology
chemical_list: D005025:Ethylene Dichlorides; D005030:Ethylenes; D009097:Multienzyme Complexes; D005018:Ethyl Chloride; C024565:ethylene dichloride; C036216:ethylene; D010088:Oxidoreductases; C023895:methyl coenzyme M methylreductase; D008780:Methyltransferases; D014805:Vitamin B 12