Table 1.
Inhibition constants (Ki) of Xaa-Tyr/Xaa-Asp dipeptides against the hydrolytic activities on synthetic substrates of S46 peptidases.
| P2 amino acid (Xaa) | H.I. of P2 aa | Ki (µM) | |||
|---|---|---|---|---|---|
| SmDPP7 | PgDPP7 | SmDPP11 | PgDPP11 | ||
| Asp | − 55 | – | – | – | – |
| Pro | − 46* | – | – | – | – |
| Glu | − 31 | – | – | – | – |
| Asn | − 28 | 7.80 ± 0.42 | 210 ± 18 | 61.9 ± 6.6 | 4.06 ± 0.16 |
| Lys | − 23 | – | – | – | – |
| Arg | − 14 | – | – | 23.2 ± 1.4 | – |
| Gln | − 10 | – | – | – | – |
| Ser | − 5 | – | – | – | – |
| Gly | 0 | – | – | – | – |
| His | 8 | – | – | – | – |
| Thr | 13 | – | – | – | – |
| Ala | 41 | – | – | – | – |
| Tyr | 63 | 7.66 ± 1.27 | – | 5.66 ± 0.23 | – |
| Met | 74 | 11.2 ± 0.4 | – | – | – |
| Val | 76 | 55.2 ± 0.5 | – | – | – |
| Trp | 97 | – | 30.6 ± 0.9 | 6.27 ± 0.18 | 1.36 ± 0.06 |
| Leu | 97 | 2.39 ± 0.08 | 61.0 ± 1.2 | 5.68 ± 0.07 | 3.35 ± 0.23 |
| Ile | 99 | – | – | – | – |
| Phe | 100 | 1.27 ± 0.06 | 150 ± 2 | 7.01 ± 0.27 | 5.11 ± 0.06 |
Xaa-Tyr and Xaa-Asp were used as competitive inhibitors for DPP7s and DPP11s, respectively, and Tyr-Tyr-MCA and Leu-Asp-MCA were used as substrates for DPP7s and DPP11s, respectively. The hydrophobicity indexes (H.I.) of the amino acids were adopted from Sereda et al. and Mohera et al.25,26.
*The hydrophobicity index of proline is normalized from Sereda et al., under the condition at pH 2.0. “–” means not determined due to low inhibitory activity. Standard deviations were obtained from three independent experiments.