nitric oxide synthase(redirected from NO synthase I)
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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 synthaseAbbreviation: 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