Final answer:
Phospholipase C is the enzyme that was instrumental in the discovery of GPI-anchored proteins, as it can release membrane proteins by cleaving the GPI anchor. It also plays a significant role in cellular signaling pathways.
Step-by-step explanation:
The enzyme phospholipase C was instrumental in the discovery of GPI-anchored proteins because it releases certain membrane proteins from the plasma membrane by cleaving specific phospholipids. GPI-anchored proteins are a class of proteins bound to the membrane by a glycosylphosphatidylinositol anchor, which phospholipase C can hydrolyze.
In the context of cellular signaling, phospholipase C cleaves PIP₂ to form diacylglycerol (DAG) and inositol triphosphate (IP3), which serve as second messengers in signal transduction. Specifically, DAG remains in the plasma membrane and activates protein kinase C (PKC), whereas IP3 diffuses into the cytoplasm to release Ca²⁺ from the endoplasmic reticulum. This release of Ca²⁺ by IP3 is a pivotal step in the transduction of many signaling pathways that affect various cellular processes.