cl03888

Phosphotyrosyl phosphatase activator (PTPA) is also known as protein phosphatase 2A (PP2A) phosphatase activator. PTPA is an essential, well conserved protein that stimulates the tyrosyl phosphatase activity of PP2A. It also reactivates the serine/threonine phosphatase activity of an inactive form of PP2A. Together, PTPA and PP2A constitute an ATPase. It has been suggested that PTPA alters the relative specificity of PP2A from phosphoserine/phosphothreonine substrates to phosphotyrosine substrates in an ATP-hydrolysis-dependent manner. Basal expression of PTPA is controlled by the transcription factor Yin Yang1 (YY1). PTPA has been suggested to play a role in the insertion of metals to the PP2A catalytic subunit (PP2Ac) active site, to act as a chaperone, and more recently, to have peptidyl prolyl cis/trans isomerase activity that specifically targets human PP2Ac.