title: Implication of manganese (III), oxalate, and oxygen in the degradation of nitroaromatic compounds by manganese peroxidase (MnP).
abstract: The fungal ligninolytic enzyme manganese peroxidase (MnP) is known to function by oxidizing Mn(II) to Mn(III), a powerful oxidant. In this work, an abiotic system consisting of Mn(III) in oxalate buffer under aerobic conditions (Mn(III)/oxalate/O2 system) was shown to be capable of extensively transforming 2-amino-4,6-dinitrotoluene (2A46DNT)--one of the main reduction products of 2,4,6-trinitrotoluene (TNT). No significant transformation occurred in the presence of other organic acids or under anaerobic conditions. The Mn(III)/oxalate/O2 system was also able to transform other nitroaromatic compounds such as 2-nitrotoluene, 4-nitrotoluene, 2,4-dinitrotoluene, TNT - the latter to a lesser extent -, and their reduction derivatives. The Mn(III)/oxalate/O2 system mineralized 14C-U-ring labeled 2A46DNT slightly, while no significant mineralization of 14C-U-ring labeled TNT was observed. Unidentified 14C-transformation products were highly polar. Electron spin resonance experiments performed on the Mn(III)/oxalate/O2 system revealed the generation of formyl free radicals (*COO-). The oxygen requirement for the transformation of nitroaromatic compounds suggests the involvement of superoxide free radicals (O2-*). produced through autoxidation of *COO- by molecular oxygen. The implication of such a Mn(III)/oxalate/O2 system in the MnP-catalyzed degradation of nitroaromatic pollutants by white-rot fungi is further discussed.
authors.affiliation: Department of Civil and Environmental Engineering, University of Iowa, Iowa City 52242, USA.
authors.forename: B
authors.initials: B
authors.lastname: Van Aken
authors.forename: S N
authors.initials: SN
authors.lastname: Agathos
mesh_terms: D000363:Agaricales / Q000201:enzymology*; D000814:Aniline Compounds / Q000378:metabolism*; D001673:Biodegradation, Environmental; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D007700:Kinetics; D008345:Manganese / Q000378:metabolism*; D009574:Nitro Compounds / Q000145:classification / Q000378:metabolism*; D010070:Oxalates / Q000737:chemistry* / Q000494:pharmacology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*
chemical_list: D000814:Aniline Compounds; D009574:Nitro Compounds; D010070:Oxalates; C035208:2-amino-4,6-dinitrotoluene; D008345:Manganese; D010544:Peroxidases; C051129:manganese peroxidase; D010100:Oxygen