PPME1, also known protein phosphatase methylesterase-1(PME1), catalyzes the demethylation and inactivation of protein phosphatase (PP2A), which is a multimeric phosphoserine/ threonine protein phosphatase associated with growth inhibition and cell cycle arrest. It can demethylate PP2A catalytic subunit in vitro and okadaic acid treatment is capable of inhibiting this reaction. It is conserved from yeast to human and contains a motif found in lipases having a catalytic triad activated serine as their active site nucleophile.