1. In E. coli, ATCase is inhibited by CTP and is activated by ATP. Explain the biological significance of these effects.
2. Explain how PALA can act as both an activator and an inhibitor of ATCase.
1. ATCase [aspartate transcarbamoylase] catalyzes the first step in pyrimidine biosynthesis. In bacteria pyrimidine nucleotide biosynthesis is regulated by a feedback inhibition. ATCase is inhibited by CTP [cytidine 5?-triphosphate], the end product of pyrimidine biosynthesis. This is an allosteric regulation.
The activation by ATP and inhibition by CTP ...
This solution includes a discussion and diagrams and mechanisms for ATCase and PALA. 210 words.