So at high concentration of ATP, the ATP will displace the CTP from the regulatory side on those regulatory chains, and that will shift the equilibrium from the T state to the R state and make the active sites much more likely to actually bind and convert that substrate molecule into the final product, the CTP. Now, the question is, what is the physiological significance of this effect? Why exactly does a high concentration of ATP activate this enzyme in the first place? Well, for two reasons. First of all, if we have a high concentration of ATP, that means we have plenty of energy inside our cells. And that implies if we have plenty of energy, we can easily use that energy to actually synthesize these nucleuside triphosphates, such as ATP, by using this enzyme right here.