Peptidyl-prolyl cis/trans isomerase (PPIase) that acts as a key virulence factor by promoting host leukocyte transformation. Binds to and isomerizes specific phosphorylated Ser/Thr-Pro (pSer/Thr-Pro) motifs in a subset of proteins, resulting in conformational changes in the proteins. Promotes host leukocyte transformation by binding to phosphorylated host FBXW7, disrupting dimerization and promoting FBXW7 autoubiquitination and subsequent degradation. Degradation of host FBXW7, leads to stabilization of JUN, which promotes cell transformation. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Directly inhibited by juglone anti-parasite drug. Not inhibited by buparvaquone anti-parasite drug. Interacts with host FBXW7; leading to FBXW7 autoubiquitination and subsequent degradation. PIN1 harbors a single amino acid variation in strains sensitive to buparvaquone (AC Q4UG71).