This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
Nitric oxide is synthesized from this amino acid: 
Select and explain. 
A. Arginine, B. Lysine, C. Leucine, D. Isoleucine
A: Arginine
Answer: A: Arginine 
Explanation: Ans. A. Arginine* Nitric oxide is synthesized from L-Arginine* Reaction is catalyzed from enzyme nitric oxide synthase.* Function:# Similar in reactive oxygen species in their function# Potent microbial killer# Produced by endothelial cells and by activated macrophages