Involved in pre-mRNA splicing as component of the spliceosome (PubMed:11991638, PubMed:28076346, PubMed:28502770, PubMed:33220177). PPIases accelerate the folding of proteins. Catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides (PubMed:16595688). Catalyzes prolyl peptide bond isomerization in CDC40/PRP17 (PubMed:33220177). Plays an important role in embryonic brain development; this function is independent of its isomerase activity (PubMed:33220177).