Nitric Oxide Synthase (NOS) catalyzes the biosynthesis of nitric oxide from L-arginine. Constitutively expressed NOS is found in brain (nNOS) and endothelial cells (eNOS). iNOS is a soluble enzyme found in a variety of tissues including macrophages, hepatocytes, vascular smooth muscle cells, and chondrocytes. iNOS expression is increased by a variety of factors including LPS, IFN-γ, Il-1β, and TNF-α, whereas expression is deceased by dexamethasone. The enzyme has been cloned from several species including mouse, rat, and human with homology of at least 80% between these species. The calculated molecular weight of the protein from the deduced amino acid sequence is 130,000 - 131,000.
