Electron-Transfer Mechanisms of Nitric-Oxide Synthase

Nitric oxide(NO)is an important molecule with many diverse biological functions as a signaling and cytotoxic molecule in the cardiovascular, nervous, and immuno systems. NO is synthesized from L-Arg by a family of enzymes termed nitric-oxide synthase(NOS). NOS is a fusion protein composed of an oxygenase domain with a cytochrome P450-like heme active site and a reductase domain similar to NADPH-cytochrome P450 reductase. Electron transfer from NADPH via the reductase domain to the heme active site is prerequisite for the activation of molecular oxygen with this enzyme. We summarized current concept of the electron transfer system of NOS based mainly on the eNOS crystal structure and our recent findings.