endothelial nitric oxide synthase (eNOS) is one of four major isoforms of nitric oxide synthase (NOS). The four isoforms, neuronal NOS, endothelial NOS, inducible NOS, and mitochondrial NOS, catalyze the synthesis of nitric oxide (NO) from L-arginine and oxygen. NO is a small free radical that functions as a key signaling molecule in the cardiovascular and neural systems. eNOS is responsible for most of the NO production in the vascular system where it mediates smooth muscle relaxation, angiogenesis, and clotting.
