Nitric oxide is synthesized from which amino acid:

NO is also called as Endothelium Derived Relaxing Factor (EDRF). NO (nitric oxide) is synthesized from arginine by enzyme NOS (Nitric oxide synthase) in the endothelial cells. It requires 5 cofactors:- NADPH FAD FMN Heme and Tetrahydrobiopterin (BH4). The vasodilator - nitroglycerin also enters smooth muscle cells, where its metabolism also leads to the formation of NO. NO synthase :-There are three isoforms of NOS (Nitric oxide synthase) 1. nNOS - neuronal 2. iNOS- inducible 3. eNOS- endothelial EC no. 1 (oxido-reductase) Mono oxygenase (one oxygen is added in substrate) Usually belongs to EC no 4 but NO synthase is an exception.