A group of intracellular enzymes that hydrolyse proteins. They are involved in the normal turnover of tissue protein, and the softening of meat when game is hung.
A calcium-dependent protease involved in the degradation of cellular protein.
A group of protein-destroying, lysosomal enzymes found in nearly every cell in the body. Many of these enzymes are released by cancer cells in excessive amounts, a factor that contributes to the invasiveness of tumors into neighboring tissues. The detection of cathepsins in tumors is strongly correlated with metastasis.