Characterization of a novel angular dioxygenase from fluorene-degrading Sphingomonas sp. strain LB126

In this study, the genes involved in the initial attack on fluorene by Sphingomonas sp. LB126 were investigated. The ? and ? subunits of a dioxygenase complex (FlnA1A2), showing 63% and 51% sequence identity respectively, with the subunits of an angular dioxygenase from Gram-positive Terrabacter sp. DBF63, were identified. When overexpressed in E. coli, FlnA1A2 was responsible for the angular oxidation of fluorene, fluorenol, fluorenone, dibenzofuran and dibenzo-p-dioxin. Moreover, FlnA1A2 was able to oxidize polycyclic aromatic hydrocarbons and heteroaromatics, some of which were not oxidized by the dioxygenase from Terrabacter sp. DBF63. Quantification of resulting oxidation products showed that fluorene and phenanthrene were preferred substrates.