PPIases accelerate the folding of proteins. Substrate specificity carried out with 'Suc-Ala-Xaa-Pro-Phe-4-nitroanilide', where Xaa is the amino acid tested, was found to be Phe > Leu >> Ile > Lys = Ala > Trp > His >> Gln (By similarity). [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Belongs to the FKBP-type PPIase family.