Allosteric regulation is important in many biological processes, including cell 
signaling, gene regulation, and metabolism. Saccharomyces cerevisiae chorismate 
mutase (ScCM) is a key homodimeric enzyme in the shikimate pathway responsible 
for the generation of aromatic amino acids, where it is allosterically inhibited 
and activated by Tyr and Trp, respectively. Our previous studies indicated that 
binding of both allosteric effectors is negatively cooperative, that is binding 
at one allosteric binding site discourages binding at the other, due to the 
entropic penalty of binding the second allosteric effector. We utilized variable 
temperature isothermal titration calorimetry (ITC) and nuclear magnetic 
resonance (NMR) experiments to better understand the entropic contributions to 
allosteric effector binding, including changes to solvent entropy and protein 
conformational entropy. Upon binding either Tyr or Trp, ScCM experiences a 
quenching of motions on the picosecond-to-nanosecond time scale, which we could 
relate to a loss of protein conformational entropy. Further ITC and NMR studies 
were consistent with the Tyr-bound form of ScCM being associated with more water 
molecules compared to the Trp-bound form and Tyr binding being associated with a 
less positive solvent entropy change. These studies provide insight into the 
role of structural dynamics in ScCM function and highlight the importance of 
solvent entropy changes in allosteric regulation, a historically 
underappreciated concept.