AbstractPeptidyl‐prolyl‐cis‐trans isomerase catalyzes the interconversion of the cis and trans isomers of the proline‐containing polypeptides and the folding process of proteins. This protein was known to be cyclophilin which has high binding affinity for cyclosporin A, a cyclic undecapeptide of fungal origin with potent immunosuppressive property agent. The two cytosolic peptidyl‐prolyl‐isomerases were found from Fusarium sporotrichioides. The amino acid sequence of the major peptidyl‐prolyl isomerase a was determined by conventional sequencing methods; the protein with a calculated molecular mass of 19.7 kDa consisting of 179 amino acids. The comparison of the amino acid sequence of peptidyl‐prolyl‐isomerase from Fusarium with that of Nucerospora crassa revealed a significant degree of amino acid sequence homology (82.2%).