Fig. 2.

A, dilution protocol for determination of reversibility: 870 ng/ml cathepsin L and 25 nM inhibitor were combined and incubated at room temperature. B, reversibility data for CID 23631927 after 0 (○), 15 min (△), 1 h (□), and 4 h (▲) of preincubation with cathepsin L and upon 100-fold dilution into assay buffer containing 1 μM Z-Phe-Arg-AMC as substrate, and the final inhibitor concentration was 0.25 nM. A full enzyme-substrate reaction without inhibitor (●) served as a positive control. C, enlarged reaction progress curve with 4-h preincubation of cathepsin L and CID 23631927 to clearly demonstrate the recovering rate of enzymatic cleavage of the substrate.