Minireview: Calcium-dependent proteolysis in living cells

Calcium ion, one of the second messengers in living organisms, has various functions including the ability to enhance intracellular proteolysis. This calcium-dependent proteolysis occurs in the cytosol or membrane rather than in the lysosome. Its mode of action is very wide, including cleavage of hormone receptors, activation of regulatory enzymes and limited proteolysis of the cytoskeletal structure. Although contradictory, the biochemical evidence implies a specified regulatory function of it in the cell. The activation mechanism of a purified calcium-dependent proteinase ( EC 3.4.22.- ) is also discussed.