eNOS (Endothelial NOS) is a nitric oxyde synthase enzyme, part of the Nitric oxyde pathway. Nitric oxide synthases (NOS) are enzymes that catalyze the generation of nitric oxide (NO) from L-arginine and require nicotinamide adenine dinucleotide phosphate (NADPH) as a cofactor. At least three isioforms of NOS have been idenified: neuronal NOS (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS). NOS-3 (eNOS, endothelial NOS) produces NO which is implicated in vascular smooth muscle relaxation through a cGMP-mediated signal transduction pathway. NO mediates vascular endothelial growth factor (VEGF)-induced angiogenesis in coronary vessels and promotes blood clotting through the activation of platelets.