The serine/threonine protein phosphatase 2A catalytic subunit alpha isoform (PP2A alpha) modulates the activity of phosphorylase B kinase casein kinase 2,Mouse,itogen-stimulated S6 kinase, and MAP-2 kinase. PP2A alpha dephosphorylates the SV40 large T antigen and p53, dephosphorylates the SV40 large T antigen,Porcinereferentially on serine residues 120, 123, 677, and perhaps 679. PP2A consists of a common heterodimeric cire enzyme composed of a 36 kDa catalytic subunit (subunit C) and a 65 kDa constant regulatory subunit (subunit A) that associates with a variety of regulatory subunits. The C subunit is the most active, followed by the AC form, which is more active than the ABC form, and activity of all three forms is strongly stimulated by manganese, and to a lesser e, Xenopus/Amphibian,tent by magnesium. This antibody reacts with the catalytic subunit (subunit C).