Cathepsin

Cathepsin enzymes are a family of proteases found primarily in the lysosomes of cells, where they are involved in protein degradation and turnover. These enzymes play a crucial role in various cellular processes including apoptosis, autophagy, and immune responses. Cathepsins are classified into several types based on their active site structure and substrate specificity, including cathepsins B, D, L, and K, among others. Each type has specific functions; for instance, cathepsin K is key in bone resorption, making it a target for osteoporosis treatments. The activity of cathepsins is tightly regulated, as their dysregulation is associated with pathological conditions such as cancer, arthritis, and neurodegenerative diseases.