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Títol:
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Novel Antioxidant Role of Alcohol Dehydrogenase E from Escherichia coli
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Autor/a:
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Echave Lozano, Pedro; Tamarit Sumalla, Jordi; Cabiscol Català, Elisa; Ros Salvador, Joaquim
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Notes:
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Alcohol dehydrogenase E (AdhE) is an Fe-enzyme
that, under anaerobic conditions, is involved in dissimilation
of glucose. The enzyme is also present under
aerobic conditions, its amount is about one-third and its
activity is only one-tenth of the values observed under
anaerobic conditions. Nevertheless, its function in the
presence of oxygen remained ignored. The data presented
in this paper led us to propose that the enzyme
has a protective role against oxidative stress. Our results
indicated that cells deleted in adhE gene could not
grow aerobically in minimal media, were extremely sensitive
to oxidative stress and showed division defects. In
addition, compared with wild type, mutant cells displayed
increased levels of internal peroxides (even
higher than those found in a katG strain) and increased
protein carbonyl content. This pleiotropic phenotype
disappeared when the adhE gene was reintroduced
into the defective strain. The purified enzyme
was highly reactive with hydrogen peroxide (with a Ki of
5 M), causing inactivation due to a metal-catalyzed oxidation
reaction. It is possible to prevent this reactivity
to hydrogen peroxide by zinc, which can replace the
iron atom at the catalytic site of AdhE. This can also be
achieved by addition of ZnSO4 to cell cultures. In such
conditions, addition of hydrogen peroxide resulted in
reduced cell viability compared with that obtained
without the Zn treatment. We therefore propose that
AdhE acts as a H2O2 scavenger in Escherichia coli cells
grown under aerobic conditions.
This work was funded by Grants BMC2001-0874 from Ministerio de Ciencia y Tecnología (Spain) and 2000 SGR 0042 from Generalitat de Catalunya (Spain). |
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Drets:
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(c) The American Society for Biochemistry and Molecular Biology, 2003
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Tipus de document:
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article
publishedVersion |
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Publicat per:
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American Society for Biochemistry and Molecular Biology
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