Inhibition studies with NSK4-77 and NSK5-15. (A) NSK4-77 was used at 0 nM (○), 100 nM (□), 200 nM (▿), and 400 nM (♢). (B) NSK5-15 was used at 0 nM (○), 50 nM (□), 100 nM (▿), and 200 nM (♢). The enzymatic activity of PK was assayed as described in Materials and Methods. The data shown are derived from one of two experiments performed in triplicate. Error bars indicate ranges of values within the single experiment shown.