Cathepsin D is a lysosomal aspartic protease, an enzyme that plays a pivotal role in the degradation of intracellular proteins. Lysosomes, the cellular organelles where cathepsin D resides, are responsible for the breakdown and recycling of various substrates within the cell. Cathepsin D is unique among the cathepsin family due to its aspartic protease activity, whereas most other cathepsins are cysteine proteases. This enzyme is involved in various physiological processes, including the activation and degradation of enzymes, processing of hormones and growth factors, and the breakdown of proteins under certain conditions.
Cathepsin D inhibitors are molecules designed to specifically target and reduce the enzymatic activity of cathepsin D. These inhibitors often function by binding to the active site of the enzyme or altering its conformation, thereby preventing it from interacting with its protein substrates. Given the crucial role of cathepsin D in protein catabolism within the lysosome, its inhibition can have profound effects on cellular processes.