Table 2. Inhibitory Properties of SFTI-1, SFTI-FCQR and SFTI-FCQR Residue 14 Variants.
| Enzyme | Inhibitor | IC50 (nM) | K i (nM) | Morrison K i (nM) | Theoretical Mass | Determined Mass | Substrate (100 µM) |
| KLK4 | SFTI-FCQR Asn14 | 0.0635±0.0024 | - | 0.0386±0.0060 | 1559.75 | 1560.40 | FVQRpNA |
| SFTI-FCQR Tyr14 | 3.47± 0.20 | - | 2.55±0.43 | 1610.77 | 1610.56 | ||
| SFTI-FCQR Lys14 | 6.07±0.13 | - | 3.56±0.27 | 1573.80 | 1574.93 | ||
| SFTI-FCQR Asp14 | 7.97±1.08 [16] | 3.62±0.26 | 3.89±0.40 | 1560.73 | 1559.94 | ||
| SFTI-FCQR Gly14 | 14.74±1.089 | - | 10.39±2.87 | 1502.73 | 1504.77 | ||
| SFTI-FCQR Ala14 | 26.23±0.85 | - | 18.31± 3.36 | 1516.74 | 1517.99 | ||
| SFTI-FCQR Ser14 | 29.23±1.081 | - | 21.24 ±3.81 | 1532.74 | 1533.94 | ||
| SFTI-1 | 221±10.1 [16] | - | - | 1514.75 | 1514.84 | ||
| KLK14 | SFTI-FCQR Asp14 | 1506±37.1 [16] | - | - | - | - | Ac-GSLR-pNA |
| SFTI-FCQR Asn14 | 251± 21.9 | - | - | - | - | ||
| β-Trypsin | SFTI-FCQR Asp14 | 4064±109 [16] | - | - | - | - | BAPNA |
| SFTI-FCQR Asn14 | 2178±145 | - | - | - | - | ||
| SFTI-1 | - | 0.1 [17] | - | - | - | ||
| Matriptase | SFTI-FCQR Asn14 | >10,000 | - | - | - | - | Bz-FVRpNA |
| SFTI-1 | - | 0.92 [19] | - | - | - | N-t-Boc-QAR-AMC | |
| Thrombin | SFTI-FCQR Asn14 | >10,000 | - | - | - | - | Bz-FVRpNA |
| SFTI-1 | - | 5050 [19] | - | - | - | N-t-Boc-LRR-AMC | |
| Chymotrypsin | SFTI-FCQR Asn14 | >10,000 | - | - | - | - | WpNA |
| SFTI-1 | - | 2300±100 [51] | - | - | - | N-succinyl-AAPPpNA |
Amino acids are represented by the one letter code.