title: Dimethylsulfide:acceptor oxidoreductase from Rhodobacter sulfidophilus. The purified enzyme contains b-type haem and a pterin molybdenum cofactor.
abstract: Dimethylsulfide:receptor oxidoreductase was purified from the purple non-sulfur phototrophic bacterium Rhodobacter sulfidophilus. The native form of the enzyme had a molecular mass of 152 kDa and was composed of three distinct subunits of 94, 38 and 32 kDa. Dimethylsulfide:acceptor oxidoreductase did not oxidise other thioethers which were tested. The enzyme was able to reduce a variety of N-oxides using reduced methylviologen as electron donor but it reduced dimethylsulfoxide at a very low rate. The resting form of dimethylsulfide:acceptor oxidoreductase exhibited a spectrum which was characteristic of a reduced cytochrome with absorbance maxima at 562 nm, 533 nm and 428 nm. Pyridine haemochrome analysis established that the cytochrome contained a b-type haem and a content of 0.65 mol protohaem/mol enzyme was determined. After oxidation of the haem with ferricyanide, the absorbance spectrum of the reduced cytochrome was restored by reduction with dimethylsulfide. Metal analysis revealed that dimethylsulfide:acceptor oxidoreductase contained 0.5 mol Mo and 3.5 mol Fe/mol enzyme. Heat treatment of the enzyme released material with fluorescence excitation and emission spectra which were characteristic of form B of the pterin component of the pterin molybdenum cofactor. From this analysis it is concluded that dimethylsulfide:acceptor oxidoreductase is a molybdenum oxotransferase which may also contain a iron-sulfur cluster. It is suggested that the haem and pterin molybdenum cofactor are associated with the 94-kDa subunit.
authors.affiliation: Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich, UK.
authors.forename: S P
authors.initials: SP
authors.lastname: Hanlon
authors.forename: T H
authors.initials: TH
authors.lastname: Toh
authors.forename: P S
authors.initials: PS
authors.lastname: Solomon
authors.forename: R A
authors.initials: RA
authors.lastname: Holt
authors.forename: A G
authors.initials: AG
authors.lastname: McEwan
mesh_terms: D002845:Chromatography; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003067:Coenzymes / Q000032:analysis; D004121:Dimethyl Sulfoxide / Q000378:metabolism; D017886:Durapatite; D004591:Electrophoresis, Polyacrylamide Gel; D006418:Heme / Q000032:analysis*; D007700:Kinetics; D046911:Macromolecular Substances; D008667:Metalloproteins / Q000032:analysis*; D008970:Molecular Weight; D008982:Molybdenum / Q000032:analysis*; D000090006:Molybdenum Cofactors; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D011621:Pteridines / Q000032:analysis*; D016992:Rhodobacter / Q000201:enzymology* / Q000254:growth & development; D013053:Spectrophotometry; D013379:Substrate Specificity
chemical_list: D003067:Coenzymes; D004121:Dimethyl Sulfoxide; D017886:Durapatite; D006418:Heme; D046911:Macromolecular Substances; D008667:Metalloproteins; D008982:Molybdenum; D000090006:Molybdenum Cofactors; D010088:Oxidoreductases; D011621:Pteridines; C022261:molybdopterin; C100768:dimethylsulfide - acceptor oxidoreductase