Table 1. Trypsin inhibitory activities of SdPI and its mutants.
| Protein | WT | K12A | G13F | K14A | A15F |
| Inhibition constant, (Ki) (M) | 1.6×10−7 | 2.9×10−7 | 2.6×10−7 | - | 6.2×10−5 |
The inhibitory activities of SdPI and its mutants on the hydrolysis of synthetic chromogenic substrates by trypsin were assayed in 100 mM Tris-HCl (pH 8.0), containing 10 mM CaCl2 at 25°C. Trypsin was pre-incubated with the inhibitor for 30 min. The reaction was initiated by addition of synthetic chromogenic substrates. Formation of p-nitroaniline was monitored continuously at 405 nm for 5 min. Inhibition constants of SdPI and mutants were determined by Lineweaver-Burk plots and further replotting of the slopes. Errors in Ki values are less than ± 10%.
-, no inhibition detected.