IMPDHbt (A) and IMPDHlpp (B) activity versus IMP concentration.

<p>Enzyme activity was determined at a fixed concentration of NAD (2 mM for IMPDHbt and 6 mM for IMPDHlpp), and in the absence (red curve) or in the presence (blue curve) of 5 mM MgATP. The curves correspond to the fit of the experimental data to the Michaelis-Menten equation for IMPDHbt and Hill equation for IMPDHlpp and the calculated parameters are displayed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116578#pone.0116578.t005" target="_blank">Table 5</a>.