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Journal of Bacteriology, August 1998, p. 3823-3827, Vol. 180, No. 15
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
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
; 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.
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