Calpain is a family of calcium-dependent proteases that play a crucial role in various cellular processes, including cell signaling, differentiation, and apoptosis. These enzymes are activated by the presence of calcium ions and are involved in the breakdown of specific proteins, which can influence cellular functions and responses. Calpain is found in many tissues throughout the body, including muscle and brain. It is implicated in several physiological and pathological conditions, such as neurodegenerative diseases and cardiovascular disorders. Understanding calpain's mechanisms can provide insights into potential therapeutic targets for these conditions.