The enzymes responsible for the degradation of isopropylbenzene (IPB) and co-oxidation of trichloroethene (TCE) by BD2 are encoded by the linear plasmid pBD2. Fragments containing IPB catabolic genes were cloned from pBD2 and the nucleotide sequence was determined. By means of database searches and expression of the cloned genes in recombinant strains, we identified five clustered genes, which encode the three components of the IPB 2,3-dioxygenase system, reductase (), ferredoxin () and the two subunits of the terminal dioxygenase (), as well as the 3-isopropylcatechol (IPC) 2,3-dioxygenase (). The protein sequences deduced from the gene cluster exhibited significant homology with the corresponding proteins of analogous degradative pathways in Gram-negative and Gram-positive bacteria, but the gene order differed from most of them. IPB 2,3-dioxygenase and 3-IPC 2,3-dioxygenase could both be expressed in but the IPB 2,3-dioxygenase activities were too low to be detected by polarographic and TCE degradative means. However, inhibitor studies with the BD2 wild-type are in accordance with the involvement of the IPB 2,3-dioxygenase in TCE oxidation.


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