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Modeling the role of covalent enzyme modification in Escherichia coli nitrogen metabolism.

ABSTRACT: In the bacterium Escherichia coli, the enzyme glutamine synthetase (GS) converts ammonium into the amino acid glutamine. GS is principally active when the cell is experiencing nitrogen limitation, and its activity is regulated by a bicyclic covalent modification cascade. The advantages of this bicyclic-cascade architecture are poorly understood. We analyze a simple model of the GS cascade in comparison to other regulatory schemes and conclude that the bicyclic cascade is suboptimal for maintaining metabolic homeostasis of the free glutamine pool. Instead, we argue that the lag inherent in the covalent modification of GS slows the response to an ammonium shock and thereby allows GS to transiently detoxify the cell, while maintaining homeostasis over longer times.

SUBMITTER: Kidd PB

PROVIDER: S-EPMC3894576 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Modeling the role of covalent enzyme modification in Escherichia coli nitrogen metabolism.

Kidd Philip B PB Wingreen Ned S NS

Physical biology 20100107 1

In the bacterium Escherichia coli, the enzyme glutamine synthetase (GS) converts ammonium into the amino acid glutamine. GS is principally active when the cell is experiencing nitrogen limitation, and its activity is regulated by a bicyclic covalent modification cascade. The advantages of this bicyclic-cascade architecture are poorly understood. We analyze a simple model of the GS cascade in comparison to other regulatory schemes and conclude that the bicyclic cascade is suboptimal for maintaini ...[more]

PMID: 20057006

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