This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
[{'content': 'The main enzyme responsible for activation of xenobiotics is \nSelect and explain. \nA. Cytochrome P - 450, B. Glutathione S - transferase, C. NADPH cytochrome P - 450 reductase, D. Glucoronyl transferase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Cytochrome P450 (CYP) enzymes in extrahepatic tissues often play a dominant role in target tissue metabolic activation of xenobiotic compounds. They may also determine drug efficacy and influence the tissue burden of foreign chemicals or bioavailability of therapeutic agents.', 'role': 'assistant'}]