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J. Biol. Chem., Vol. 275, Issue 45, 34853-34857, November 10, 2000
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,
-Dicarbonyl Compounds in the Toxicity of
Short Chain Sugars*
From the Department of Biochemistry, Duke University Medical
Center, Durham, North Carolina 27710
The extent to which sugars serve as targets for
superoxide was examined using glycolaldehyde as the simplest sugar and
using superoxide dismutase (SOD)-replete and SOD-null strains growing under aerobic and anaerobic conditions. Glycolaldehyde was more toxic
to the SOD-null strain than to its SOD-replete parent, and this
differential effect was oxygen-dependent. The product,
glyoxal, could be trapped in the medium by 1,2-diaminobenzene and
assayed as quinoxaline. The SOD-null strain produced more glyoxal and eliminated it more slowly than the SOD-replete parent strain. Glyoxal
was ~10 times more toxic than glycolaldehyde and was more toxic to
the SOD-null strain than to the parental strain. 1,2-Diaminobenzene protected against the toxicity of glycolaldehyde. These
Escherichia coli strains contained the
glutathione-dependent glyoxalases I and II, as well as the
glutathione-independent glyoxalase III. Of these enzymes, glyoxalase
III was most abundant, and it was inactivated within the aerobic
SOD-null strain and also in extracts when exposed to the flux of
superoxide and hydrogen peroxide imposed by the xanthine oxidase
reaction. Thus, it appears that short chain sugars are oxidized by
superoxide yielding toxic dicarbonyls. Moreover, the defensive
glyoxalase III is also inactivated by the oxidative stress imposed by
the lack of SOD, thereby exacerbating the deleterious effect of
sugar oxidation.
To whom correspondence should be addressed. Tel.: 919-684-5122;
Fax: 919-684-8885; E-mail: fridovich@biochem.duke.edu.
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