3) Ribose is the initial substrate for the synthesis of AMP and GMP (purine nucleotides and the precursors of ATP and GTP respectively). The following diagram is a simplified overview of this overall metabolic pathway. The numbers refer to enzymatically-catalyzed steps in the pathway.

a) Which enzyme is most likely to be inhibited by high levels of AMP? Explain.

b) Which enzyme is most likely to be inhibited by high levels of IMP? Explain.

c) Imagine a species of animal in which the affinity of enzyme 6 for IMP is lower than the human enzyme. What effect would this have on the rate of production of GMP from IMP in the animal as compared to humans? In these animals, is IMP more or less likely to be feedback inhibiting the enzyme you identified in part b at any given time? Explain.