Proline, an imino acid, plays a crucial role in stress response across various organisms. It is involved in cellular signaling processes that promote survival or apoptosis, and its metabolism influences reactive oxygen species (ROS) production, which is linked to stress tolerance in plants, lifespan extension in worms, and apoptosis, tumor suppression, and cell survival in animals. Proline metabolism is regulated by enzymes such as P5CS, P5CR, OAT, PRODH, and P5CDH, which are involved in proline biosynthesis, degradation, and redox regulation. Proline acts as an osmolyte, chemical chaperone, metal chelator, and ROS scavenger, contributing to stress protection through various mechanisms. It also influences redox homeostasis by maintaining NADP+/NADPH ratios and supporting energy production. Proline metabolism is linked to signaling pathways that promote cell survival and regulate stress responses. The interplay between proline metabolism and ROS signaling is critical for cellular adaptation to stress. Understanding these mechanisms can enhance agricultural research and improve human health.Proline, an imino acid, plays a crucial role in stress response across various organisms. It is involved in cellular signaling processes that promote survival or apoptosis, and its metabolism influences reactive oxygen species (ROS) production, which is linked to stress tolerance in plants, lifespan extension in worms, and apoptosis, tumor suppression, and cell survival in animals. Proline metabolism is regulated by enzymes such as P5CS, P5CR, OAT, PRODH, and P5CDH, which are involved in proline biosynthesis, degradation, and redox regulation. Proline acts as an osmolyte, chemical chaperone, metal chelator, and ROS scavenger, contributing to stress protection through various mechanisms. It also influences redox homeostasis by maintaining NADP+/NADPH ratios and supporting energy production. Proline metabolism is linked to signaling pathways that promote cell survival and regulate stress responses. The interplay between proline metabolism and ROS signaling is critical for cellular adaptation to stress. Understanding these mechanisms can enhance agricultural research and improve human health.