Chemoselective nitro group reduction and reductive dechlorination initiatedegradation of 2-chloro-5-nitrophenol by Ralstonia eutropha JMP134

Ralstonia eutropha JMP134 utilizes 2-chloro-5-nitrophenol as a sole source of nitrogen, carbon, and energy. The initial steps for degradation of 2-chl oro-5-nitrophenol are analogous to those of 3-nitrophenol degradation in R. eutropha JMP134. 2-Chloro-5-nitrophenol is initially reduced to 2-chloro-5 -hydroxylaminophenol, which is subject to an enzymatic Bamberger rearrangem ent yielding 2-amino-5-chlorohydroquinone. The chlorine of 2-amino-5-chloro hydroquinone is removed by a reductive mechanism, and aminohydroquinone is formed. 2-Chloro-5-nitrophenol and 3-nitrophenol induce the expression of 3 -nitrophenol nitroreductase, of 3-hydroxylaminophenol mutase, and of the de chlorinating activity. 3-Nitrophenol nitroreductase catalyzes chemoselectiv e reduction of aromatic nitro groups to hydroxylamino groups in the presenc e of NADPH. 3-Nitrophenol nitroreductase is active with a variety of mono-, di-, and trinitroaromatic compounds, demonstrating a relaxed substrate spe cificity of the enzyme. Nitrosobenzene serves as a substrate for the enzyme and is converted faster than nitrobenzene.