This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Nitric oxide is derived from which amino acid? \nSelect and explain. \nA. Histidine, B. Lysine, C. Methionine, D. Arginine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans:D.)Arginine.NITRIC OXIDE (NO)/ENDOTHELIUM DERIVED RELAXING FACTOR (EDRF)Nitric oxide, a vasodilator is formed by the action of nitric oxide synthase on Arginine. Synthesis:NO is formed by the action of Cytosolic enzyme NO synthase in endothelial & neuronal cells.Substrate: Arginine, O 2 , NADPHCoenzyme: NADPH, FAD, FMN, Heme, tetrahydrobiopterinProduct: Citrulline, NOFeaturesReacts with oxygen & superoxide ? peroxynitrite which decomposes to form highly reactive OH-radicalIt stimulates guanyl cyclase (cGMP)FunctionsRelaxes smooth muscles Prevents platelet aggregationFunctions as neurotransmitter in brainMediates tumoricidal, bactericidal actions of macrophagesInvolved in penile erection; (sildenafil affects this process by inhibiting a cGMP dependent phosphodiesterase)', 'role': 'assistant'}]