OYE flavoprotein reductases initiate the condensation of TNT-derived intermediates to secondary diarylamines and nitrite.
Polynitroaromatic explosives such as 2,4,6-trinitrophenol (picric acid) and 2,4,6-trinitrotoluene (TNT) are toxic and recalcitrant environmental pollutants. They persist in the environment due to the highly inactivated pi system of their aromatic rings, which are inaccessible to dioxygenases that normally initiate the bacterial aerobic catabolism of (nitro-) aromatic compounds. Aside from reductive transformation of nitro side groups to hydroxylamines, trinitroarenes are prone to aromatic ring reductions by some flavin reductases to yield Meisenheimer mono and dihydride complexes. Here we show that the simultaneous accumulation of Meisenheimer complexes and aromatic hydroxylamines derived from TNT gives rise to the condensation of both types of reactive intermediates to secondary diarylamines and nitrite as the end-products of this environmentally relevant reaction sequence. As a consequence, overall mass balances of aerobic biotransformations of TNT become possible for the first time. In our study, the process of TNT activation was enzymatically initiated by the xenobiotic reductase B (XenB)-like flavin reductase of Pseudomonas putida JLR11 and then completed chemically by autodimerization. The structures of the formed end products were unequivocally elucidated by NMR.
Wittich
Rolf-Michael
RM
Departamento de Protección Ambiental, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Calle Profesor Albareda 1, E-18008 Granada, Spain. rolf.wittich@eez.csic.es
Haïdour
Ali
A
Van Dillewijn
Pieter
P
Ramos
Juan-Luis
JL
D000588:Amines / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002851:Chromatography, High Pressure Liquid; D005420:Flavoproteins / Q000378:metabolism*; D019811:Hydroxylamine / Q000378:metabolism; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D016958:Pseudomonas putida / Q000201:enzymology*; D013997:Time Factors; D014303:Trinitrotoluene / Q000737:chemistry / Q000378:metabolism*
D000588:Amines; D005420:Flavoproteins; D009573:Nitrites; D014303:Trinitrotoluene; D019811:Hydroxylamine; D009252:NADPH Dehydrogenase