Question: CTP differs from UTP by a single nitrogen atom in place of oxygen on the pyrimidine ring. What serves as the source of the nitrogen atom in the reaction catalyzed by CTP Synthetase?
Question: Why isn’t Ribose phosphate pyrophosphokinase (i.e. the enzyme for the synthesis of phosphoribosyl pyrophosphate) considered the committed step in de novo purine biosynthesis?
Question: What is the first intact purine made in de novo purine biosynthesis? What is the rate limiting step in purine biosynthesis? How is its activity regulated? How does the cell balance the synthesis of AMP and GMP?