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': 'Which inhibits adenyl cyclase enzyme? \nSelect and explain. \nA. Somatostatin, B. Calcitonin, C. Epinephrine, D. Thyroxine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Somatostatin acts directly on the acid-producing parietal cells a G-protein coupled receptor which inhibits adenylate cyclase, thus effectively antagonising the stimulatory effect of histamine to reduce acid secretion.Ref: DM Vasudevan, 7th edition', 'role': 'assistant'}]