PTEN, also referred to as MMAC phosphatase, is a tumor suppressor implicated in a wide variety of human cancers. It encodes a 403 amino acid polypeptide originally described as a dual-specificity protein phosphatase. Unlike most of the protein tyrosine phosphatases, this protein preferentially dephosphorylates phosphoinositide substrates. It negatively regulates intracellular levels of phosphatidylinositol-3,4,5-trisphosphate in cells and functions as a tumor suppressor by negatively regulating AKT/PKB signaling pathway. PTEN regulates p53 protein levels and activity and is involved in G protein-coupled signaling during chemotaxis.
