Immunophilins

In molecular biology, immunophilins are endogenous cytosolic peptidyl-prolyl isomerases that interconvert [sic] between the cis and trans positions.

Immunophilins are targeted by immunosuppressive drugs such as sirolimus, cyclosporin, and tacrolimus. For these drugs in particular, known immunophilins such as cyclophilin catalyze the cis-trans isomerization of peptide bonds, particularly X-Pro peptide bonds. This prolyl isomerase activity can be inhibited by immunosuppressive drugs.