This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Biochemistry
[{'content': 'The catabolite repression is mediated by a catabolite gene activator protein (CAP) in conjunction with: \nSelect and explain. \nA. AMP, B. GMP, C. c-AMP, D. C-GMP', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C. c-AMPAttachment of RNA polymerase to the promoter site requires the presence of a CAP bound to C-AMP. The presence of glucose lowers the intracellular concentration of c-AMP by inactivating the enzyme adenylate cyclase responsible for the synthesis of c-AMP. Therefore, the binding of RNA polymerase to DNA (due to the absence of CAP-c-AMP) and the transcription are negligible in the presence of glucose.', 'role': 'assistant'}]