Cathepsins are a group of enzymes that play a crucial role in breaking down proteins within cells. They are primarily found in lysosomes, which are cellular structures responsible for digestion and waste removal. These enzymes help in various biological processes, including tissue remodeling, immune response, and the recycling of cellular components. There are several types of cathepsins, each with specific functions. For example, cathepsin B is involved in protein degradation and has been studied for its role in diseases like cancer. Understanding cathepsins is important for developing treatments for conditions where protein breakdown is disrupted.