title: Elucidation of the metabolic pathway for dibenzothiophene desulphurization by Rhodococcus sp. strain IGTS8 (ATCC 53968).
abstract: Rhodococcus sp. strain IGTS8 (ATCC 53968) is able to utilize dibenzothiophene (DBT) as a sole source of sulphur. The carbon skeleton of DBT is not metabolized and is conserved as 2-hydroxybiphenyl (HBP), which accumulates in the medium. This phenotype is due to the expression of the plasmid-encoded DBT-desulphurization (dsz) operon, which encodes three proteins, DszA, B and C. In this paper it is shown, using [35S]DBT radiolabelling studies, that sulphur is released in the form of inorganic sulphite. The pathway of DBT desulphurization is described in detail. In summary, DszC catalyses the stepwise S-oxidation of DBT, first to dibenzothiophene 5-oxide (DBTO) and then to dibenzothiophene 5,5-dioxide (DBTO2); DszA catalyses the conversion of DBTO2 to 2-(2'-hydroxyphenyl)benzene sulphinate (HBPSi-) and DszB catalyses the desulphination of HBPSi- to give HBP and sulphite. Studies with cell-free extracts show that DszA and DszC, but not DszB, require NADH for activity. 18O2-labelling studies show that each incorporated oxygen atom is derived directly from molecular oxygen. These results are consistent with the role of DszC as a mono-oxygenase, of DszA as an apparently unique enzyme which catalyses the reductive hydroxylation of DBTO2 leading to cleavage of the thiophene ring, and of DszB as an aromatic sulphinic acid hydrolase.
authors.forename: Christopher
authors.initials: C
authors.lastname: Oldfield
authors.affiliation: Energy Biosystems Corporation, 4200 Research Forest Drive, The Woodlands, TX 77381, USA.
authors.forename: Olga
authors.initials: O
authors.lastname: Pogrebinsky
authors.affiliation: Energy Biosystems Corporation, 4200 Research Forest Drive, The Woodlands, TX 77381, USA.
authors.forename: Julie
authors.initials: J
authors.lastname: Simmonds
authors.affiliation: Energy and Environmental Research Center, University of North Dakota, Grand Forks, ND 58202, USA.
authors.forename: Edwin S
authors.initials: ES
authors.lastname: Olson
authors.affiliation: Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556-0309, USA.
authors.forename: Charles F
authors.initials: CF
authors.lastname: Kulpa
mesh_terms: D015258:Acid Rain / Q000517:prevention & control; D001673:Biodegradation, Environmental; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009876:Operon; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D011995:Recombination, Genetic; D012240:Rhodococcus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D013447:Sulfites / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism; D013876:Thiophenes / Q000378:metabolism*
chemical_list: D015258:Acid Rain; D013447:Sulfites; D013876:Thiophenes; D009243:NAD; D013455:Sulfur; D010088:Oxidoreductases; C090100:dibenzothiophene monooxygenase; C016366:dibenzothiophene