PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. Acts as a regulatory subunit for TAP42-associated PP2A-like phosphatases modulating their activity or substrate specificity, probably by inducing a conformational change in the catalytic subunit, a direct target of the PPIase. Can reactivate inactive phosphatase PP2A-phosphatase methylesterase complexes (PP2Ai) in presence of ATP and Mg(2+) by dissociating the inactive form from the complex. Acts also inhibitory at high concentrations. Involved in the regulation of cell cycle progression, mitotic spindle formation and bud morphogenesis. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Interacts with the phosphatase PP2A catalytic subunits PPH21 and PPH22. Forms a ternary complex with PPH21-TAP42. Present with 2430 molecules/cell in log phase SD medium.