ABSTRACT
Oxygen plays complexed roles in the cell. While oxygen is indispensable for an aerobic cell to obtain the essential chemical energy in the form of ATP, it is often transformed into highly reactive forms, radical oxygen intermediates (ROI), which are often toxic for the cell. In order to defend against the toxic actions of ROI, cells have acquired multiple endogenous antioxidant systems. These defense mechanisms include redox enzyme systems such as glutaredoxin and thioredoxin (Holmgren, 1985; Holmgren, 1989). Recent studies of cell biology and biochemistry have revealed the involvement of these molecules in the intracellular signal transduction pathways (Holmgren, 1985; Ziegler, 1985; Holmgren, 1989; Allen, 1993). The term "redox regulation" has thus been proposed to indicate the role of oxidoreductive modifications of proteins in regulating their functions. Oxidoreductive reaction of biomolecules, mostly proteins, which used to be considered as oxidative "stress," is now considered as a "signal" that contains biological information that is necessary for the maintenance of cellular homeostasis in response to the extracellular environment. The nature of redox regulation of one of the transcription factors, nuclear factor kappa B (NFKB) will be discussed as an example.
