|Title||Modeling the role of covalent enzyme modification in Escherichia coli nitrogen metabolism.|
|Publication Type||Journal Article|
|Year of Publication||2010|
|Authors||Kidd, PB, Wingreen, NS|
|Date Published||2010 Mar|
|Keywords||Escherichia coli, Glutamate-Ammonia Ligase, Homeostasis, Models, Biological, Models, Chemical, Nitrogen|
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.
|Alternate Journal||Phys Biol|