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) It is one of six related genes or pseudogenes found in a cluster, thought to result from gene duplication, on chromosome 1. Belongs to the cyclophilin-type PPIase family. PPIase A subfamily.