Abstract
Nitric oxide is an exceptionally stable molecule as a radical species. The smallest signal molecule is formed from oxygen and L-arginine by well-defined enzymes. Nitric oxide plays roles not only in physiological regulation such as blood pressure, platelet aggregation and neuronal function, but also in pathophysiological states. The reactions of nitric oxide with target molecules involve electron transfer. This mechanism differs essentially from those of neurotransmitters and hormones identified so far. It is reasonable to as sume that distinct signal transduction pathways are involved in this redox signal molecule. In this review, we briefly summarize nitration, nitrosation and nitrosylation of target molecules in vivo by nitric oxide.