Phospholipase D (PLD) is an enzyme that plays a crucial role in cellular signaling and membrane dynamics. It catalyzes the hydrolysis of phospholipids, specifically converting phosphatidylcholine into phosphatidic acid and choline. This process is important for various cellular functions, including cell growth, differentiation, and membrane trafficking. PLD is found in many organisms, including plants and animals, and is involved in several physiological processes. Its activity can be regulated by various factors, such as G-proteins and receptor signaling, making it a key player in the response to external stimuli. Understanding PLD's function can provide insights into cellular mechanisms and potential therapeutic targets.