Inhibitory potency of a panel of peptidyl-aldehydes against proteasome preparations
| Inhibitor/activity . | Immunoproteasome, Ki (μM) . | Constitutive proteasome, Ki (μM) . |
|---|---|---|
| Z-LLL-CHO (MG-132) | ||
| ChT-L | 5.1 ± 0.9 (6) | 6.9 ± 0.84 (6) |
| Z-FL-CHO (bortezomib-aldehyde) | ||
| ChT-L | 2.1 ± 0.29 (9) | 5.55 ± 0.47 (6) |
| Z-LnL-CHO (IPSI-001) | ||
| ChT-L | 1.03 ± 0.17 (3) | 105 ± 1.3 (3) |
| BrAAP | 1.45 ± 0.15 (8) | 239 ± 14 (6) |
| Z-FF-CHO (IPSI-002) | ||
| ChT-L | 4.0 ± 0.27 (6) | 56 ± 4.4 (3) |
| BrAAP | 1.46 ± 0.38 (9) | NI |
| Z-hFF-CHO (IPSI-003) | ||
| ChT-L | 2.74 ± 0.33 (6) | 40* |
| BrAAP | 3.19 ± 0.11 (3) | NI |
| Z-LF-CHO (IPSI-004) | ||
| ChT-L | 5.6 ± 0.2 (3) | 154* |
| BrAAP | 4.07 ± 0.17 (3) | NI |
| Z-AF-CHO (IPSI-005) | ||
| ChT-L | 24 (2) | 380 (2) |
| BrAAP | 24 (2) | NI* |
| Inhibitor/activity . | Immunoproteasome, Ki (μM) . | Constitutive proteasome, Ki (μM) . |
|---|---|---|
| Z-LLL-CHO (MG-132) | ||
| ChT-L | 5.1 ± 0.9 (6) | 6.9 ± 0.84 (6) |
| Z-FL-CHO (bortezomib-aldehyde) | ||
| ChT-L | 2.1 ± 0.29 (9) | 5.55 ± 0.47 (6) |
| Z-LnL-CHO (IPSI-001) | ||
| ChT-L | 1.03 ± 0.17 (3) | 105 ± 1.3 (3) |
| BrAAP | 1.45 ± 0.15 (8) | 239 ± 14 (6) |
| Z-FF-CHO (IPSI-002) | ||
| ChT-L | 4.0 ± 0.27 (6) | 56 ± 4.4 (3) |
| BrAAP | 1.46 ± 0.38 (9) | NI |
| Z-hFF-CHO (IPSI-003) | ||
| ChT-L | 2.74 ± 0.33 (6) | 40* |
| BrAAP | 3.19 ± 0.11 (3) | NI |
| Z-LF-CHO (IPSI-004) | ||
| ChT-L | 5.6 ± 0.2 (3) | 154* |
| BrAAP | 4.07 ± 0.17 (3) | NI |
| Z-AF-CHO (IPSI-005) | ||
| ChT-L | 24 (2) | 380 (2) |
| BrAAP | 24 (2) | NI* |
Dixon plots were used to obtain Ki values. Assays were carried out at 3 substrate concentrations and at 6 different inhibitor concentrations without preincubation of the enzyme with inhibitors, and the number of determinations is shown in parentheses. Substrate concentrations were 0.5 to 4.0 mM for the ChT-L activity using Z-GGF-pAB.
Standard single-letter abbreviations are used for amino acid residues where applicable.
ChT-L indicates chymotrypsin-like activity; BrAAP, branched-chain amino acid preferring; hF, homophenylalanine; IC50, concentration inducing 50% target inhibition; IPSI, immunoproteasome-specific inhibitor; Ki, inhibitory constant; nL, norleucinal; pAB, para-amino-benzoate; Z, carbobenzoxy; and NI, not inhibited
IC50 instead of Ki.