Peptidyl‐prolyl cis‐trans isomerase from Bacillus subtilis A prokaryotic enzyme that is highly sensitive to cyclosporin A

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Abstract
Cyclophylins are members of a class of proteins with peptidyl‐protyl cis‐trans isomerase activity. These enzymes bind the immunosuppressive agent, cyclosporin A (CsA), which acts as a competitive inhibitor. The peptidyl‐prolyl cis‐trans isomerase from Bacillus subtilis (PPlase) was purified to homogeneity in a 4‐step purification procedure, which resulted in a 100‐fold protein purification with a yield of 5%, Coomassie blue‐stained SDS‐PAGE revealed a single band of about 18 kDa. PPlase activity was determined using synthetic peptides as substrates in a 2‐step reaction coupled to chymotrypsin. Treatment of Bacillus subtilis PPlase by CsA revealed an inhibition constant of K 1=175 nM, which differs from cyclophilin of enterobacteria such as E. coli or Salmonella typhimurium and is in the range of human enzymes.