Has the potential to contribute to the immunosuppressive and toxic effects of FK506 and rapamycin. PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. {ECO:0000269|PubMed:7513996, ECO:0000269|PubMed:7592869}. This is the function of ENSG00000119782 (FKBP1B, FKBP prolyl isomerase 1B).