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Aromatic nitroreductase from the basidiomycete Phanerochaete chrysosporium
S Rieble1, D K Joshi, M H Gold
1Department of Chemistry, Biochemistry, and Molecular Biology, Oregon Graduate Institute of Science & Technology, Portland 97291-1000.
Biochemical and Biophysical Research Communications
|November 30, 1994
Summary
A novel membrane-associated nitroreductase enzyme was discovered in Phanerochaete chrysosporium. This enzyme reduces various nitroaromatic compounds under anaerobic conditions, with potential applications in bioremediation.
Area of Science:
- Biochemistry
- Environmental Microbiology
- Fungal Metabolism
Background:
- Phanerochaete chrysosporium is a white-rot fungus known for its lignin-degrading capabilities.
- Nitroaromatic compounds are common environmental pollutants often requiring bioremediation.
- Enzymatic reduction of nitroaromatics is a key step in their biodegradation.
Purpose of the Study:
- To identify and characterize a membrane-associated enzyme in Phanerochaete chrysosporium responsible for nitroaromatic reduction.
- To investigate the substrate specificity and optimal reaction conditions for this enzyme.
- To explore the potential role of this enzyme in the degradation of nitroaromatic pollutants.
Main Methods:
- Cell-free extracts of Phanerochaete chrysosporium were prepared.
- Enzyme activity was assayed by monitoring the reduction of various nitroaromatic compounds.
- Reaction products were identified and quantified using High-Performance Liquid Chromatography (HPLC) and Gas Chromatography-Mass Spectrometry (GC-MS).
- Enzyme properties such as optimal pH, temperature, and cofactor requirements were determined.
Main Results:
- A membrane-associated aromatic nitroreductase activity was identified.
- The enzyme efficiently reduced several nitroaromatic compounds, including dinitrobenzene and trinitrotoluene derivatives.
- Hydroxylamines and amines were identified as reduction products, with nitroso and hydroxylamino intermediates observed.
- Optimal activity was observed at pH 6.5 and 50°C under anaerobic conditions.
- The enzyme required NAD(P)H as a cosubstrate and could be solubilized by Triton X-100.
Conclusions:
- Phanerochaete chrysosporium possesses a membrane-bound nitroreductase capable of detoxifying nitroaromatic compounds.
- This enzyme functions optimally under anaerobic conditions and utilizes NAD(P)H.
- The characterization of this enzyme provides insights into fungal bioremediation pathways for nitroaromatic pollutants.