Rieske non-heme iron oxygenase (RO) family, Ortho-halobenzoate-1,2-dioxygenase (OHBDO)-like subfamily, N-terminal Rieske domain of the oxygenase alpha subunit; composed of the oxygenase alpha subunits of OHBDO, salicylate 5-hydroxylase (S5H), terephthalate 1,2-dioxygenase system (TERDOS) and similar proteins. 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. OHBDO converts 2-chlorobenzoate (2-CBA) to catechol as well as 2,4-dCBA and 2,5-dCBA to 4-chlorocatechol, as part of the chlorobenzoate degradation pathway. Although ortho-substituted chlorobenzoates appear to be particularly recalcitrant to biodegradation, several strains utilize 2-CBA and the dCBA derivatives as a sole carbon and energy source. S5H converts salicylate (2-hydroxybenzoate), a metabolic intermediate of phenanthrene, to gentisate (2,5-dihydroxybenzoate) as part of an alternate pathway for naphthalene catabolism. S5H is a multicomponent enzyme made up of NagGH (the oxygenase components), NagAa (the ferredoxin reductase component), and NagAb (the ferredoxin component). The oxygenase component is made up of alpha (NagG) and beta (NagH) subunits. TERDOS is present in gram-positive bacteria and proteobacteria where it converts terephthalate (1,4-dicarboxybenzene) to protocatechuate as part of the terephthalate degradation pathway. The oxygenase component of TERDOS, called TerZ, is a hetero-hexamer with 3 alpha (TerZalpha) and 3 beta (TerZbeta) subunits.
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