Elucidation of the metabolic pathway for dibenzothiophene desulphurization by Rhodococcus sp. strain IGTS8 (ATCC 53968)

作者：Oldfield C; Pogrebinsky O; Simmonds J; Olson ES; Kulpa CF

来源：Microbiology-SGM, 1997, 143: 2961-2973.

• Rhodococcus sp. strain IGTS8
• fossil fuel desulphurization
• clean technologies
• desulphurizing enzymes

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 (dsr) operon, which encodes three proteins, DszA, B and C. In this paper it is shown, using [S-35]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. O-18(2)-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.

• 出版日期1997-9