v5.1.0.3
Cicer data from the Legume Information System
Type | Family |
Description | Nitric oxide synthase ( ) (NOS) enzymes produce nitric oxide (NO) by catalyzing a five-electron oxidation of a guanidino nitrogen of L-arginine (L-Arg). Oxidation of L-Arg to L-citrulline occurs via two successive monooxygenation reactions producing N(omega)-hydroxy-L-arginine as an intermediate. 2 mol of O(2) and 1.5 mol of NADPH are consumed per mole of NO formed [].Arginine-derived NO synthesis has been identified in mammals, fish, birds, invertebrates, plants, and bacteria [ ]. Best studied are mammals, where three distinct genes encode NOS isozymes: neuronal (nNOS or NOS-1), cytokine-inducible (iNOS or NOS-2) and endothelial (eNOS or NOS-3) []. iNOS and nNOS are soluble and found predominantly in the cytosol, while eNOS is membrane associated. The enzymes exist as homodimers, each monomer consisting of two major domains: an N-terminal oxygenase domain, which belongs to the class of haem-thiolate proteins, and a C-terminal reductase domain, which is homologous to NADPH:P450 reductase (). The interdomain linker between the oxygenase and reductase domains contains a calmodulin (CaM)-binding sequence. NOSs are the only enzymes known to simultaneously require five bound cofactors animal NOS isozymes are catalytically self-sufficient. The electron flow in the NO synthase reaction is: NADPH -->FAD -->FMN -->haem -->O(2). eNOS localisation to endothelial membranes is mediated by cotranslational N-terminal myristoylation and post-translational palmitoylation [ ]. The subcellular localisation of nNOS in skeletal muscle is mediated by anchoring of nNOS to dystrophin. nNOS contains an additional N-terminal domain, the PDZ domain [].This entry represents all forms of NOS from eukaryotes. For further information see [ , , , ]. |
Short Name | NOS_euk |