The kinetics of the AT Case reaction were examined using inc

The kinetics of the AT Case reaction were examined using increasing concentrations of aspartate, in the presence and absence of CTP and ATP as shown in Figure 16.2. What information can you obtain by looking at the shapes of the curves in this figure? What kinetic parameter s) change in the presence of CTP? What parameter(s) do not change? What is the significance of these observations? Answer question 2b for ATP.

Solution

Answer a & b:

Aspartate Transcarbamoylase is an allosteric enzyme invoved in biochemical reaction and forms Cytidine triphosphate (CTP). This enzyme reaction is controlled by the process of feedback inhibition. Feedback inhibition is the process in which the product CTP inhibit the enzyme ATCase by binding of CTP to ATCase enzyme other than the active site of that enzyme. Enzyme can exist in either tense atate or relax state. CTP stabilises the tense state of the enzyme ATCase and it becomes difficult for the substrate to bind to the ATCase for the conversion of relaxed state and so the curve shown in the graph is shifted to the right. Hence, CTP is an inhibitor for the enzyme ATCase.

Answer c:

ATP is an activator of the enzyme ATCase as it stabilises the relaxed state of enzyme and it becomes easier for the substrate to bind to the enzyme and so the curve shown in the graph is shifted towards the left. Hence, ATP is an activator of enzyme ATCase.

Reference:

https://www.ncbi.nlm.nih.gov/books/NBK22460/