Effect of truncated HK peptides on the binding of kallikrein to HK. HK peptides, either (A) C-terminal truncated or (B) N-terminal truncated (4.5 μmol/L), were incubated with a single concentration of kallikrein (2.9 nmol/L) in HK-coated wells for 2 hours. After washing, the activity of bound kallikrein was determined using chromogenic substrate S2302 (0.4 mmol/L). The activity of the control experiment in which no HK peptides were added was considered to be 100%. The data shown are the mean ± SEM of three experiments.