CHEMBL3707943

Enzymatic Assay: Cyclophilin PPlase activity was measured at 20 C. by using the standard chymotrypsin coupled assay (Kofron J L, Kuzmic P, Kishore V, Colon-Bonilla E, Rich D H. Determination of kinetic constants for peptidyl prolyl cis-trans isomerases by an improved spectrophotometric assay. Biochemistry. 1991 Jun. 25; 30(25):6127-34). The assay buffer (25 mM Hepes, 100 mM NaCl, pH 7.8) and CypA, B or D (1900 nM stock solution) were pre-cooled to 4 C., to which then was added 5 uL of 50 mg/ml chymotrypsin in 1 mM HCl. The reaction was initiated by adding 20 uL of 3.2 mM peptide substrate (Suc-Ala-Ala-cis-Pro-Phe-pNA) in LiCl/TFE solution with rapid inversion. After a delay from the onset of mixing, the absorbance of p-nitroaniline was followed at 390 nM until the reaction was complete (1 min). The final concentration of LiCl in the assay was 20 mM; TFE was present at a concentration of 4% (v/v). Absorbance readings were collected every 1 s by spectrophotometer.