Rieske non-heme iron oxygenase (RO) family, Biphenyl dioxygenase (BPDO)-like subfamily, N-terminal Rieske domain of the oxygenase alpha subunit; composed of the oxygenase alpha subunits of BPDO and similar proteins including cumene dioxygenase (CumDO), nitrobenzene dioxygenase (NBDO), alkylbenzene dioxygenase (AkbDO) and dibenzofuran 4,4a-dioxygenase (DFDO). ROs comprise a large class of aromatic ring-hydroxylating dioxygenases that enable microorganisms to tolerate and utilize aromatic compounds for growth. The oxygenase alpha subunit contains an N-terminal Rieske domain with an [2Fe-2S] cluster and a C-terminal catalytic domain with a mononuclear Fe(II) binding site. The Rieske [2Fe-2S] cluster accepts electrons from a reductase or ferredoxin component and transfers them to the mononuclear iron for catalysis. BPDO degrades biphenyls and polychlorinated biphenyls (PCB's) while CumDO degrades cumene (isopropylbenzene), an aromatic hydrocarbon that is intermediate in size between ethylbenzene and biphenyl. NBDO catalyzes the initial reaction in nitrobenzene degradation, oxidizing the aromatic rings of mono- and dinitrotoluenes to form catechol and nitrite. NBDO belongs to the naphthalene subfamily of ROs. AkbDO is involved in alkylbenzene catabolism, converting o-xylene to 2,3- and 3,4-dimethylphenol and ethylbenzene to cis-dihydrodiol. DFDO is involved in dibenzofuran degradation.
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