How do we know that there exists a biological molecule inside our body that is used to basically control the activity of this enzyme? Well, the first evidence that this is an allosteric enzyme came from early studies that basically showed that the rate of formation of this and carbon as pertain depends on the concentration of this final product, the CTP. And this is described in the following graph. So we have the Y axis is the rate of formation of the M carbon oil aspartate and the x axis is the concentration of this final product in this reaction here, the CTP, the citadine triphosphate. So what this curve basically shows us, what the blue curve tells us is when inside our cells we have a low concentration of citadine triphosphate, the rate of formation of this intermediate will be relatively high. And so what that implies is the activity of the atcase that aspartate transcarbomolase will also be high.