PIN: Proteins and Enzymes

Nitric oxide (NO) is a pleiotropic signaling molecule implicated in diverse biological processes including inhibition of platelet aggregation, regulation of neurotransmission, vasodilation, immune responses, and inflammation. NO is synthesized from L-arginine and O2 by three nitric oxide synthase (NOS) enzymes termed endothelial NOS (eNOS), neuronal NOS (nNOS), and inducible NOS (iNOS). Each enzyme isoform is expressed in a variety of tissues and cell types. While eNOS and nNOS generally exhibit constitutive expression and are involved in physiological signaling and maintenance functions, iNOS expression is induced by inflammatory stimuli and is associated with both normal and pathological immune responses.