<prompt> No is synthesized from:L-arginineL-citrullineGlycineLysine  <response>: Also called asEndothelium derived Relaxing Factor NO nitric oxide: - synthesized fromArginineby enzymeNOSNitric oxide synthase in the endothelial cells Nitric oxide relaxes the smooth muscles of blood vessels The vasodilator - nitroglycerin also enters smooth muscle cells, where its metabolism also leads to the formation of NO. There are three isoforms of NOS Nitric oxide synthase n NOS - neuronal i NOS- inducible e NOS- endothelial 