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Previous experiments resulted in the cloning of the ferredoxin gene fdx1 and the reductase A2 gene redA2 of the electron transport system of the dioxin dioxygenase of Sphingomonas sp. strain RW1 and characterized the corresponding proteins. Fdx1 was found to be clustered with genes that appeared to encode two atypical decarboxylases and a glutathione-S transferase. A study was conducted to identify the open reading frames encoding the dioxin diogenase itself and derived functional expression of this enzyme system.

The dbfB gene of the enzyme 2,2', 3-trihydroxybiphenyl dioxygenase, a monomeric protein, is cloned from a cosmid library of the Sphingomonas strain which degrades dibenzofuran and dibenzo-p-dioxin. Kinetic evaluation of the enzyme yields similar K(m) values for 2,3-dihydroxybiphenyl and 2,2',-3-trihydroxybiphenyl.