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Robustness in Glyoxylate Bypass Regulation Guy Shinar1

Summary: Robustness in Glyoxylate Bypass Regulation
Guy Shinar1
*, Joshua D. Rabinowitz2
, Uri Alon1
1 Departments of Molecular Cell Biology and Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel, 2 Department of Chemistry and Lewis-Sigler
Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
The glyoxylate bypass allows Escherichia coli to grow on carbon sources with only two carbons by bypassing the loss of
carbons as CO2 in the tricarboxylic acid cycle. The flux toward this bypass is regulated by the phosphorylation of the enzyme
isocitrate dehydrogenase (IDH) by a bifunctional kinase­phosphatase called IDHKP. In this system, IDH activity has been
found to be remarkably robust with respect to wide variations in the total IDH protein concentration. Here, we examine
possible mechanisms to explain this robustness. Explanations in which IDHKP works simultaneously as a first-order kinase
and as a zero-order phosphatase with a single IDH binding site are found to be inconsistent with robustness. Instead, we
suggest a robust mechanism where both substrates bind the bifunctional enzyme to form a ternary complex.
Citation: Shinar G, Rabinowitz JD, Alon U (2009) Robustness in Glyoxylate Bypass Regulation. PLoS Comput Biol 5(3): e1000297. doi:10.1371/journal.pcbi.1000297
Editor: Jason A. Papin, University of Virginia, United States of America
Received August 4, 2008; Accepted January 21, 2009; Published March 6, 2009
Copyright: ß 2009 Shinar et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: GS and UA were supported by the Kahn Family Foundation. JDR was supported by the National Science Foundation (Grant MCB-0643859) and the


Source: Alon, Uri - Departments of Molecular Cell Biology & Physics of Complex Systems, Weizmann Institute of Science
Rabinowitz, Joshua D. - Lewis-Sigler Institute for Integrative Genomics & Department of Molecular Biology, Princeton University


Collections: Biology and Medicine; Biotechnology