Cathepsin protease

Cathepsin proteases are a family of lysosomal enzymes primarily responsible for intracellular protein degradation but also play key roles in extracellular matrix remodeling and cell signaling. They are classified mainly by their catalytic mechanism into cysteine proteases (such as cathepsins B, L, S), serine proteases, and aspartic proteases (such as cathepsin D). These enzymes are synthesized as inactive precursors that become activated under acidic conditions within lysosomes or specialized cellular compartments. Dysregulation of specific cathepsins is implicated in numerous diseases including cancer progression/metastasis through enhanced matrix breakdown; cardiovascular disorders via vascular remodeling; neurodegeneration through amyloid processing; inflammatory conditions; infections where they facilitate pathogen entry or replication; and bone diseases such as osteoporosis via collagen degradation by osteoclast-secreted cathepins K. Several small-molecule inhibitors have been developed against individual family members with varying clinical success. Note: The term "Cathepsin protease" is overly broad—there are many distinct human cathepins with different biological functions and therapeutic relevance. For structured data extraction or drug development purposes it is essential to specify the particular member(s) involved—e.g., "Cathepin B," "Cathepsein K," etc.—rather than using the generic class name alone.

Other names

CathepsinsCysteine cathepsinsLysosomal proteases (includes specific members such as Cathepsin B, L, S, K, D)

Drugs targeting cathepsins typically act as **enzyme inhibitors**, blocking the active site or modulating activity to prevent substrate cleavage. This can reduce extracellular matrix degradation in cancer or bone resorption in osteoporosis.