The A subunit of protein phosphatase 2A serves as a scaffolding molecule to coordinate the assembly of the catalytic subunit and a variable regulatory B subunit. Involved during developmental process such as seedling and floral developments. Seems to act as a negative regulator of PP2A catalytic activity. Associates with the serine/threonine-protein phosphatase PP2A catalytic subunit C and regulatory subunit B' to positively regulates beta-oxidation of fatty acids and protoauxins in peroxisomes by dephosphorylating peroxisomal beta-oxidation-related proteins (PubMed:25489022). PP2A consists of a common heterodimeric core 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 such as subunits B (the R2/B/PR55/B55, R3/B''/PR72/PR130/PR59 and R5/B'/B56 families) (By similarity). Interacts with B'THETA (PubMed:25489022). Interacts with SRK2E/OST1 (PubMed:26175513). Interacts with SIC/RON3 (PubMed:26888284). Interacts with B'THETA in the cytosol and peroxisomal import occurs by a piggybacking transport. A number of isoforms are produced. According to EST sequences. Ubiquitous, with higher levels in roots and flowers (at protein level). Each HEAT repeat appears to consist of two alpha helices joined by a hydrophilic region, the intrarepeat loop. The repeat units may be arranged laterally to form a rod-like structure (By similarity). Belongs to the phosphatase 2A regulatory subunit A family.