PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Binds cyclosporin A (CsA). CsA mediates some of its effects via an inhibitory action on PPIase. Produced by alternative initiation. Produced by alternative splicing. This isoform is found in the cell following 22 hours growth in dark. Belongs to the cyclophilin-type PPIase family.