**5. The occurrence of the glutathione in the nucleus; active transport, de novo synthesis, diffusion or something else**

How GSH enters the nucleus and how it is regulated during the different phases of the cell cycle is still a matter of debate. The regulation of such interactions is also unclear. According to Smith and colleagues (Smith et al., 1996), the possible biochemical mechanisms responsible for the turnover of nuclear GSH are the following: 1.GSH may be taken up from the cytoplasm into the nuclei either passively or through energy-dependent processes 2.GSH may be synthesized *de novo* in the nucleus by the enzymes glutamate cysteine ligase and GSH synthetase 3.GSH may function to transport -glu-cys-cys.
