PMID:9721297

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Citation

Helling, RB (1998) Pathway choice in glutamate synthesis in Escherichia coli. J. Bacteriol. 180:4571-5

Abstract

Escherichia coli has two primary pathways for glutamate synthesis. The glutamine synthetase-glutamate synthase (GOGAT) pathway is essential for synthesis at low ammonium concentration and for regulation of the glutamine pool. The glutamate dehydrogenase (GDH) pathway is important during glucose-limited growth. It has been hypothesized that GDH is favored when the organism is stressed for energy, because the enzyme does not use ATP as does the GOGAT pathway. The results of competition experiments between the wild-type and a GDH-deficient mutant during glucose-limited growth in the presence of the nonmetabolizable glucose analog alpha-methylglucoside were consistent with the hypothesis. Enzyme measurements showed that levels of the enzymes of the glutamate pathways dropped as the organism passed from unrestricted to glucose-restricted growth. However, other conditions influencing pathway choice had no substantial effect on enzyme levels. Therefore, substrate availability and/or modulation of enzyme activity are likely to be major determinants of pathway choice in glutamate synthesis.

Links

PubMed PMC107469

Keywords

Ammonia/metabolism; Energy Metabolism; Escherichia coli/enzymology; Escherichia coli/growth & development; Escherichia coli/metabolism; Glucose/metabolism; Glutamate Dehydrogenase/metabolism; Glutamate-Ammonia Ligase/metabolism; Glutamates/biosynthesis; Phosphates/metabolism

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