Converging catabolism of 2,4,6-trinitrophenol (picric acid) and 2,4-dinitrophenol by Nocardioides simplex FJ2-1A

Initial F420-dependent hydrogenation of 2,4,6-trinitrophenol(picric acid) generated the hydride σ-complex of picrate and finally the dihydride complex.With 2,4-dinitrophenol the hydride σ-complex of 2,4-dinitrophenolis generated. The hydride transferring enzyme system showed activity against several substituted2,4-dinitrophenols but not with mononitrophenols. A Km-value of0.06 mM of the hydride transfer for picrate as substrate was found. The pH optimaof the NADPH-dependent F420 reductase and for the hydride transferase were 5.5and 7.5, respectively. An enzymatic activity has been identified catalyzing the releaseof stoichometric amounts of 1 mol nitrite from 1 mol of the dihydride σ-complexof picrate. This complex was synthesized by chemical reduction of picrate and characterizedby 1H and 13C NMR spectroscopy. The hydride σ-complex of 2,4-dinitrophenolhas been identified as the denitration product. The nitrite-eliminating activitywas enriched and clearly separated from the hydride transferring enzyme system byFPLC. 2,4-Dinitrophenol has been disproven as a metabolite of picrate (Ebert et al. 1999)and a convergent catabolic pathway for picrate and 2,4-dinitrophenol with thehydride σ-complex of 2,4-dinitrophenol as the common intermediate has been demonstrated.