The enzyme consists of linked oxygenase and reductase domains. The eukaryotic enzyme binds FAD, FMN, heme (iron protoporphyrin IX) and tetrahydrobiopterin, and its two domains are linked via a regulatory calmodulin-binding domain. Upon calcium-induced calmodulin binding, the reductase and oxygenase domains form a complex, allowing electrons to flow from NADPH via FAD and FMN to the active center. The reductase domain of the enzyme from the bacterium Sorangium cellulosum utilizes a [2Fe-2S] cluster to transfer the electrons from NADPH to the active center. cf. EC 18.104.22.168, nitric-oxide synthase (flavodoxin).
EC 22.214.171.124 created 1992, modified 2012, modified 2017