f Elucidation of the metabolic pathway for dibenzothiophene desulphurization by Rhodococcus sp. strain IGTS8 (ATCC 53968)
- Authors: Christopher Oldfield†, Olga Pogrebinsky, Julie Simmonds, Edwin S. Olson, Charles F. Kulpa
- Author for correspondence: Christopher Oldfield. Tel: + 44 131 455 2217. Fax: +44 131 455 2291. e-mail: email@example.com
- Microbiology, September 1997 143: 2961-2973, doi: 10.1099/00221287-143-9-2961
- Subject: Biochemistry
- Published Online:
Summary: 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.
Present address: Department of Biological Sciences, Napier University, Edinburgh EH 10 5DT, UK.
- Keyword(s): clean technologies, desulphurizing enzymes, Rhodococcus sp, fossil fuel desulphurization, strain IGTS8
© Society for General Microbiology 1997 | Published by the Microbiology Society
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