Final answer:
GTP (guanosine triphosphate) allosterically activates pyrimidine synthesis, ensuring a balance with purine nucleotide levels. It is part of the essential regulatory mechanisms that maintain a balance between the synthesis of nucleotides in cells.
Step-by-step explanation:
The purine triphosphate that allosterically activates pyrimidine synthesis is GTP (guanosine triphosphate). In the context of purine and pyrimidine metabolism, regulation is crucial to maintain a balance between the synthesis of purines and pyrimidines. Purine biosynthesis employs a feedback inhibition mechanism where the first committed step is generally irreversible, and regulated by the end products of the pathway.
Pyrimidine synthesis on the other hand is regulated at its committed step by the enzyme aspartate transcarbamoylase, which is inhibited by the pyrimidine end product, CTP (cytidine triphosphate). However, GTP serves as an activator in the regulation of pyrimidine synthesis, ensuring a balance with purine nucleotide levels. This emphasizes the interconnections and regulatory mechanisms that exist between the synthesis of nucleotides in cellular metabolism.