The Cysteine Protease family includes many members, such as papain and caspases. Their active sites contain cysteine residues that catalyze the hydrolysis of peptide bonds through a thiol group. These enzymes are widely located inside and outside cells, involved in protein degradation, apoptosis, and signal transduction, among other physiological processes. Gene expression is tissue-specific and can change during different developmental stages or disease states. Mutations are associated with various diseases, including cancer and neurodegenerative diseases.