Cystatin A is a type of protein known as a cysteine protease inhibitor. It plays a crucial role in regulating the activity of enzymes that break down proteins, helping to maintain balance in various biological processes. This protein is found in many tissues and is particularly abundant in the salivary glands and epithelial cells. Research has shown that cystatin A may be involved in protecting cells from damage and inflammation. Abnormal levels of this protein have been linked to certain diseases, including cancer and neurodegenerative disorders. Understanding cystatin A's functions can provide insights into potential therapeutic approaches for these conditions.