Folding of barstar C40A/C82A/P27A and catalysis of the peptidyl‐prolylcis/transisomerization by human cytosolic cyclophilin (Cyp18)

Refolding of b*C40A/C82A/P27A is comprised of several kinetically detectable folding phases. The slowest phase in refolding originates from trans-->cis isomerization of the Tyr47-Pro48 peptide bond being in cis conformation in the native state. This refolding phase can be accelerated by the peptidyl-prolyl cis/trans isomerase human cytosolic cyclophilin (Cyp18) with a kcat/K(M) of 254,000 M(-1) s(-1). The fast refolding phase is not influenced by the enzyme.