NO is a short-lived free radical and a very small compound that diffuses freely within cells from its
site of formation to its site of action. The biosynthesis of NO in the organism is carried out from Larginine
and molecular oxygen utilizing NADPH as an electron donor and using heme, FMN, FAD and
tetrahydrobiopterin (H4B) as cofactors through a reaction that consumes five electrons. The overall
reaction consists of a two step oxidative conversion of L-arginine to NO and L-citrulline via Nw-
hydroxy-L-arginine (NOHarginine) as an intermediate, with monooxygenase I and monooxygenase II,
each step representing a mixed-function oxidation