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Participation of the Entner–Doudoroff pathway in Escherichia coli strains with an inactive phosphotransferase system (PTS Glc+) in gluconate and glucose batch cultures

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Abstract:

The activity of the enzymes of the central metabolic pathways has been the subject of intensive analysis; however, the Entner–Doudoroff (ED) pathway has only recently begun to attract attention. The metabolic response to edd gene knockout in Escherichia coli JM101 and PTS Glc+ was investigated in gluconate and glucose batch cultures and compared with other pyruvate kinase and PTS mutants previously constructed. Even though the specific growth rates between the strain carrying the edd gene knockout and its parent JM101 and PTS Glc+ edd and its parent PTS Glc+ were very similar, reproducible changes in the specific consumption rates and biomass yields were obtained when grown on glucose. These results support the participation of the ED pathway not only on gluconate metabolism but on other metabolic and biochemical processes in E. coli. Despite that gluconate is a non-PTS carbohydrate, the PTS Glc+ and derived strains showed important reductions in the specific growth and gluconate consumption rates. Moreover, the overall activity of the ED pathway on gluconate resulted in important increments in PTS Glc+ and PTS- Glc+ pykF mutants. Additional results obtained with the pykA pykF mutant indicate the important contribution of the pyruvate kinase enzymes to pyruvate synthesis and energy production in both carbon sources.Key words: Escherichia coli, gluconate metabolism, Entner-Doudoroff pathway, PT system, pyruvate kinase isoenzymes.

L'activité des enzymes des voies du métabolisme central a été l'objet d'une analyse intensive; cependant, la voie d'Entner–Doudoroff (ED) commence seulement à attirer l'attention. La réponse métabolique des souches d'Escherichia coli JM101 et PTS Glc+ ayant une ablation du gène edd a été examinée en culture en milieu non renouvelé (batch) en présence de gluconate et de glucose et comparée à celle d'autres mutants de la pyruvate kinase et PTS préalablement construits. Même si les taux de croissance spécifiques des souches JM101 et PTS Glc+ edd ayant subi l'ablation du gène edd étaient très similaires à ceux de leurs souches parentales JM101 et PTS Glc+, des changements reproductibles dans les taux de consommation spécifiques ainsi que dans la production de biomasse ont été obtenus lors de la croissance en milieu contenant du glucose. Ces résultats suggèrent la participation de la voie ED, non seulement dans le métabolisme du gluconate, mais aussi dans d'autres processus métaboliques et biochimiques chez E. coli. Malgré le fait que le gluconate soit un hydrate de carbone non-PTS, les souches PTS Glc+ et les souches dérivées affichaient des réductions importantes des taux de croissance et de consommation spécifiques de gluconate. Qui plus est, l'activité globale de la voie ED sur le gluconate a augmenté de façon importante chez les mutants PTS Glc+ et PTS Glc+ pykF. Des résultats supplémentaires obtenus chez les mutants pykA pykF révèlent une contribution importante des enzymes pyruvate kinase à la synthèse du pyruvate et à la production d'énergie sur les deux sources de carbone.Mots clés : Escherichia coli, métabolisme du gluconate, voie d'Entner–Doudoroff, système PT, isoenzymes de la pyruvate kinase.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: November 1, 2005

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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