Figure 4From: Low plasma citrulline levels are associated with acute respiratory distress syndrome in patients with severe sepsisSchematic of a nitric oxide synthase (NOS) dimer with both the oxygenase and reductase domains shown. Coupling of electron transfer between these domains leads to synthesis of nitric oxide (NO). When uncoupled, NOS preferentially catalyzes the production of superoxide ion from reduction of molecular oxygen rather than NO. Uncoupling of NOS can be caused by oxidative stress, ischemia reperfusion and substrate deficiency. Arg, arginine; FMN, flavin mononucleotide binding domain; FAD, flavin adenine dinucleotide binding domain; NADPH, nicotinamide adenine dinucleotide phosphate.Back to article page