nitric oxide synthase

(redirected from Nitric oxide synthase type iii)
Also found in: Encyclopedia.

ni·tric ox·ide syn·thase (NO syn·thase, NOS),

an enzyme that catalyzes the reaction of l-arginine with 2O2 and 1.5NADPH to form NO, l-citrulline, 1.5NADP+, and 2H2O; there are an inducible and two constitutive forms of this enzyme: the constitutive forms play significant roles in regulating vascular tone, tissue blood flow, renal function, and others; in bone, brain, endothelium, granulocytes, pancreatic Z-cells, and peripheral nerves, the constitutive forms depend on calcium-calmodulin; in brain, the enzyme is cytosolic; in endothelium, it is membrane bound; the inducible form of the enzyme (for example, by endotoxin) in hepatocytes, Kupffer cells, macrophages, and smooth muscle is not calmodulin dependent.

nitric oxide synthase

Abbreviation: NOS
An enzyme that synthesizes nitric oxide from arginine; present in the central nervous system, the lining of blood vessels, the heart, joints, some autonomic neurons, and other organs.
See also: synthase

nitric oxide synthase

One of three enzymes that catalyze the synthesis of NITRIC OXIDE in blood vessel ENDOTHELIUM, nerve fibres and MACROPHAGES. These enzymes are coded for, respectively, on chromosomes 7, 12 and 17. They act by splitting off a nitrogen atom from the amino acid L-arginine which is then combined with an oxygen atom from molecular oxygen to form NO.