Kinetics of purified PiCyPA cyclophilin. It catalysed hydrolysis of N-succinyl-ala-ala-pro-phe-p-nitroanilidine (peptidyl prolyl cis-trans isomerase or PPIase activity) (A). The dependence of rate constant on the cyclophilin concentration (B). Effect of cyclophilin inhibitor, CsA, on PPIase activity of purified cyclophilin. The data represent the PPIase activity as percent of uninhibited control (C). Determination of inhibition constant of purified CyPA for CsA (D). First order rate constant was analysed using GraFit 4.0 software. Inhibition constant (ki) for CsA was determined as gradient of the line of the best fit from a plot of [CsA]/(1-k/ko) against k/ko, where k is the rate constant at any given CsA concentration and ko is the rate constant in the absence of CsA. The slope of the line represents the ki. Data represent the means SDs of three independent experiments (n = 3).