GSNO is considered an intracellular NO donor in transnitrosylation reactions. Ozone fumigation highly modulated the S-nitroso-proteome. Overall, the S-nitrosylation pattern of 28 proteins was significantly affected. The fact that we observed both S-nitrosylation and de-nitrosylation events upon ozone stress seems to be contradictory to the accumulation of nitrite and SNO that we measured in response to ozone. However, two other studies also show this phenomenon: despite an increase in SNO in Brassica juncea plants undergoing low temperature stress, Abat and Deswal identified nine proteins undergoing enhanced S-nitrosylation and eight proteins becoming de-nitrosylated. A similar trend was observed following salt stress. Similarly, the extent of S-nitrosylation in any UNC0638 protein will depend on the rates of Snitrosylation and de-nitrosylation. Recent observations classify GSNO reductase and the thioredoxin/thioredoxin reductase system as denitrosylases. The NO production/turnover and the NO targets for S-nitrosylation may be spatially or temporally separated. The kinetics and the localization of the NO production in leaves as measured by NO-specific fluorophores demonstrated that the NO production begins within the chloroplasts and subsequently propagates into the nucleus and the cytosol. The stress-dependent activation of de-nitrosylases could provide another explanation for de-nitrosylation events in the presence of enhanced NO and nitrite concentrations. In the case of phosphorylation, the phosphorylation status of proteins depends on the activities of kinases and phosphatases. These enzymes might themselves be regulated by NO. Lithocholic acid Moreover, denitrosylation is not exclusively enzymatically driven. Non-enzymatic de-nitrosylation can occur due to alterations in the cellular redox environment. S-nitrosylation events can alter the outcome of a signaling pathway by switching on/off target proteins.