Mammalian cells do not survive in the absence
of redox reactions; oxidation and reduction predominate in the swamp of
metabolic biochemical reactions inside the cell. In a situation which is less
stoichiometric, subtle alterations of the redox status in the intracellular environment
also have significant impacts on cell biology. Changes in the intracellular
redox status can be assessed by quantifying the reduction potentials of various
intracellular redox couples.
However, in practice, the motto “redox
environment” used by cell biologists usually means the relative abundance of
reactive oxygen species (ROS) inside or in proximity of a cell. More than three
decades ago people have observed that mammalian cells can actively produce ROS,
and utilize these molecules to regulate cell functions.
Then it has been discovered that in
prokaryotes, some transcription factors switch on and off their DNA binding
activity by directly sensing the presence of per oxidant ROS molecules such as
superoxide and hydrogen peroxide, which regulate gene expressions. This
phenomenon was also observed in mammalian cells.
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