Dynamics and Design Principles of a Basic Regulatory Architecture Controlling Metabolic Pathways
Figure 1
A Summary of the Leucine, Valine, and Isoleucine Biosynthesis Pathway in S. cerevisiae
Enzymes are labeled next to their respective reactions, indicated by dark green arrows for the leucine and valine biosynthesis pathways, and light green for the isoleucine pathway. Metabolites are shown as blue circles, with the final end products and the key intermediate αIPM labeled on the figure. Allosteric regulation of enzymes by end products is shown by the black lines. The transcription factors Gcn4 and Leu3 are shown as boxes, with arrows to the genes displaying the fact that they are thought to potentially regulate all the genes in the pathway. Leu3 activity is dependent on αIPM level, as shown by the red arrow. For completeness, we include the arrow showing that Leu3 expression is thought to be Gcn4-dependent. See the text for further description on how the pathway is thought to be activated under starvation conditions.