PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides (By similarity). [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Highly expressed in brain, ovary and mammary gland. Moderately expressed in lung, salivary gland, kidney, skin, adipose tissue, intestine and spleen. Weakly expressed in skeletal muscle, liver and stomach. Expressed in pleiomorphic and undifferentiated liposarcomas, osteosarcomas and breast carcinomas. 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.