Dependence of the kd on pH for binding of the N-terminal truncated peptides (A) and the C-terminal truncated peptides (B) of HK 31 to kallikrein. After adjustment of buffer pH, the ability of peptides to inhibit the binding of kallikrein to immobilized HK was determined using an amidolytic assay. kd values were obtained as described in the Materials and Methods. Each kd is a mean of at least triplicate determinations.