anti-PP2A-α/β, mAb (13D4)

Protein Phosphatase 2A (PP2A) is a ubiquitous and conserved Serine/Threonine phosphatase and accounts for a large fraction of phosphatase activity in eukaryotic cells. PP2A plays an important role in cell cycle regulation, cell growth control, development, regulation of various signal transduction pathways, and cell mobility. PP2A comprises A and B subunits which are regulatory and a catalytic C subunit. When the PP2A catalytic C subunit (36 kDa) associates with the regulatory A (65 kDa, PR65) and B subunits (PR55, PR56, PR72, PR93 etc), wide variety of heterotrimeric holoenzymes are produced with distinct functions and characteristics. The different association of the subunits give PP2A large regulatory flexibility and differential substrate specificity. The A subunit exists as two isoforms ( α and β ) as does the C subunit, whereas the B subunits fall into three families designated B, B' (also called B56), and B''. The A subunit is the scaffold required for the formation of the heterotrimeric complex and the binding of A subunit alters the enzymatic activity of the catalytic subunit, even if the B subunit is absent. PP2A can modulate the activity of phosphorylase B kinase casein kinase 2, mitogen-stimulated S6 kinase, and MAP-2 kinase. Can dephosphorylate SV40 large T antigen and p53. Dephosphorylates SV40 large T antigen, preferentially on serine residues 120, 123, 677, and perhaps 679. The C subunit was most active, followed by the AC form, which was more active than the ABC form, and activity of all three forms was strongly stimulated by manganese, and to a lesser extent by magnesium. Dephosphorylation by the AC form, but not C or ABC form is inhibited by small T antigen.