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Journal of Bacteriology, August 1998, p. 3823-3827, Vol. 180, No. 15
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Purification and Characterization of EDTA Monooxygenase from the EDTA-Degrading Bacterium BNC1

Jason W. Payne,1,2 Harvey Bolton Jr.,2 James A. Campbell,3 and Luying Xun1,2,*

Department of Microbiology, Washington State University, Pullman, Washington 99164-4233,1 and Environmental Microbiology Group2 and Advanced Organic Analytical Methods Group,3 Pacific Northwest National Laboratory, Richland, Washington 99352

Received 23 December 1997/Accepted 26 May 1998

The synthetic chelating agent EDTA can mobilize radionuclides and heavy metals in the environment. Biodegradation of EDTA should reduce this mobilization. Although several bacteria have been reported to mineralize EDTA, little is known about the biochemistry of EDTA degradation. Understanding the biochemistry will facilitate the removal of EDTA from the environment. EDTA-degrading activities were detected in cell extracts of bacterium BNC1 when flavin mononucleotide (FMN), NADH, and O2 were present. The degradative enzyme system was separated into two different enzymes, EDTA monooxygenase and an FMN reductase. EDTA monooxygenase oxidized EDTA to glyoxylate and ethylenediaminetriacetate (ED3A), with the coconsumption of FMNH2 and O2. The FMN reductase provided EDTA monooxygenase with FMNH2 by reducing FMN with NADH. The FMN reductase was successfully substituted in the assay mixture by other FMN reductases. EDTA monooxygenase was purified to greater than 95% homogeneity and had a single polypeptide with a molecular weight of 45,000. The enzyme oxidized both EDTA complexed with various metal ions and uncomplexed EDTA. The optimal conditions for activity were pH 7.8 and 35°C. Kms were 34.1 µM for uncomplexed EDTA and 8.5 µM for MgEDTA2-; this difference in Km indicates that the enzyme has greater affinity for MgEDTA2-. The enzyme also catalyzed the release of glyoxylate from nitrilotriacetate and diethylenetriaminepentaacetate. EDTA monooxygenase belongs to a small group of FMNH2-utilizing monooxygenases that attack carbon-nitrogen, carbon-sulfur, and carbon-carbon double bonds.

* Corresponding author. Mailing address: Department of Microbiology, Washington State University, Pullman, WA 99163-4233. Phone: (509) 335-2787. Fax: (509) 335-1907. E-mail: xun{at}mail.wsu.edu.

Journal of Bacteriology, August 1998, p. 3823-3827, Vol. 180, No. 15
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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