Furthermore a direct thiol protective role of
Furthermore, a direct thiol protective role of S-nitrosylation has been reported in animals . Here, formation of higher order irreversible oxidative modifications, such as sulfinic and sulfonic acids were prevented by S-nitrosylation. All these observations underline the important role of ROS in fine-tuning the activity of GSNOR and as consequence the levels of NO/SNO, which induce protective mechanisms against oxidative stress.
The different protective functions of.NO/SNO resulting from ROS-dependent inhibition of GSNOR are summarized in Fig. 3. Oxidative inhibition of GSNOR resulted in increase in cellular SNOs and induction of.NO‐dependent signaling mechanisms, resulting in GSH accumulation, enhanced activity of GSH-related renin inhibitor and finally in a protection against oxidative stress.
Concluding remarks The constitutive expression and predominant presence of GSNOR in nearly all plant tissues/cells demonstrate the important role of this enzyme for plant growth and development and for response to environmental changes and would justify to designating GSNOR as housekeeping gene/protein. Although its redox-regulation has been described mainly on the biochemical level using recombinant GSNOR, in-vivo experiments with GSNOR Cys-mutants could give information about the regulatory function of redox-sensitive cys residues in-vivo. Moreover, it is becoming more and more obvious that cells do not function as homogenous redox systems, but rather that each subcellular compartment has its own redox systems. These are depending on the compartment-specific sources of reactive oxygen and nitrogen species and on locally interacting enzymes and anti-oxidant systems. Such “high resolution” analyses of cellular redox systems are future challenges, which are essential for detailed understanding of cellular redox processes and the function of GSNOR. Furthermore, the function of GSNOR in cross-talk between the different redox-compartments during redox-signaling events is a very interesting research area that should be tackled in the near future in order to better understand the regulation of plant development and cellular responses to environmental changes.
Acknowledgements This work was supported by the Bundesministerium für Bildung und Forschung.