Document Detail

The NprA nitroreductase required for 2,4-dinitrophenol reduction in Rhodobacter capsulatus is a dihydropteridine reductase.
MedLine Citation:
PMID:  18355323     Owner:  NLM     Status:  MEDLINE    
The Rhodobacter capsulatus nprA gene codes for a putative nitroreductase. A recombinant His(6)-NprA protein was overproduced in Escherichia coli and purified by affinity chromatography. This protein contained FMN and showed nitroreductase activity with a wide range of nitroaromatic compounds, such as 2-nitrophenol, 2,4-dinitrophenol, 2,6-dinitrophenol, 2,4,6-trinitrophenol (picric acid), 2,4-dinitrobenzoate and 2,4-dinitrotoluene, and with the nitrofuran derivatives nitrofurazone and furazolidone. NADPH was the main electron donor and the ortho nitro group was preferably reduced to the corresponding amino derivative. The apparent K(m) values of NprA for NADPH, 2,4-dinitrophenol, picric acid and furazolidone were 40 microM, 78 microM, 72 microM and 83 microM, respectively, at pH and temperature optima (pH 6.5, 30 degrees C). Escherichia coli cells overproducing the NprA protein were much more sensitive to the prodrug 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954) used in cancer therapy than non-transformed cells. NprA showed the highest activity with the quinonoid form of 6,7-dimethyl-7,8-dihydropterine as substrate, so that NprA may be involved in the synthesis of tetrahydrobiopterin in R. capsulatus. Expression of a transcriptional nprA-lacZ gene fusion was induced by phenylalanine or tyrosine, but not by other amino acids like glutamate or alanine. Furthermore, both nitroreductase activity and phenylalanine assimilation were inhibited in vivo by ammonium. A mutant defective in the nprA gene showed better growth rate with Phe or Tyr as nitrogen source than the wild-type strain, although both strains showed similar growth in media with Glu or without added nitrogen. These results suggest that the NprA nitroreductase may act in vivo as a dihydropteridine reductase involved in aromatic amino acids metabolism.
Eva Pérez-Reinado; María Dolores Roldán; Francisco Castillo; Conrado Moreno-Vivián
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-03-18
Journal Detail:
Title:  Environmental microbiology     Volume:  10     ISSN:  1462-2920     ISO Abbreviation:  Environ. Microbiol.     Publication Date:  2008 Nov 
Date Detail:
Created Date:  2008-10-31     Completed Date:  2008-12-17     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100883692     Medline TA:  Environ Microbiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  3174-83     Citation Subset:  IM    
Departamento de Bioquímica y Biología Molecular, Edificio Severo Ochoa, Universidad de Córdoba, Córdoba, Spain.
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MeSH Terms
2,4-Dinitrophenol / metabolism*
Bacterial Proteins / genetics,  isolation & purification,  metabolism*
Cloning, Molecular
Coenzymes / analysis
Dihydropteridine Reductase / chemistry,  genetics,  isolation & purification,  metabolism*
Escherichia coli / genetics
Flavin Mononucleotide / analysis
Gene Deletion
Gene Expression
Gene Expression Regulation, Bacterial
Gene Expression Regulation, Enzymologic
Hydrogen-Ion Concentration
NADP / metabolism
Recombinant Proteins / biosynthesis,  chemistry,  genetics,  isolation & purification
Rhodobacter capsulatus / enzymology*,  genetics
Substrate Specificity
Reg. No./Substance:
0/Bacterial Proteins; 0/Coenzymes; 0/Recombinant Proteins; 146-17-8/Flavin Mononucleotide; 51-28-5/2,4-Dinitrophenol; 53-59-8/NADP; EC Reductase

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