Lysosomal cysteine protease

Lysosomal cysteine proteases are a family of papain-like enzymes found within the lysosomes of virtually all eukaryotic cells[3][5][8]. Their main function is the degradation of intracellular and endocytosed proteins within the acidic environment of the lysosome[3][5]. Prominent members include Cathepsins B, L, S, K, and H, each with distinct substrate and tissue localizations but often overlapping biological functions[1][2][3]. They are synthesized as zymogens and activated by proteolytic cleavage in acidic compartments[3][5]. Lysosomal cysteine proteases play key roles in antigen processing/presentation, bone remodeling, apoptosis, ECM turnover, and innate immunity[2][6][7]. Dysregulation or overexpression is associated with diseases such as cancer, cardiovascular disease, inflammatory disorders, osteoporosis, neurodegeneration, and various infections[4][7]. They are validated drug targets, but therapeutic intervention faces safety and selectivity challenges due to their redundancy and essential physiological roles[2][5][6].

Other names

Cathepsins (Cathepsin B, Cathepsin L, Cathepsin S, Cathepsin K, Cathepsin H, etc.)

Inhibition of proteolytic enzymatic activity Blockade of antigen processing (via cathepsin S inhibition) Reduced extracellular matrix degradation (e.g., in atherosclerosis or osteoporosis)