Cysteine cathepsins belong to the papain-like family C1 of clan CA cysteine peptidases.
These enzymes are ubiquitously expressed and exert their proteolytic activity mainly, but not
exclusively within the compartments along the endocytic pathway. Moreover, cysteine
cathepsins are active in pericellular environments as soluble enzymes or bound to cell
surface receptors at the plasma membrane, and possibly even within secretory vesicles, the
cytosol, mitochondria, and within the nuclei of eukaryotic cells. Proteolytic actions performed …