Table 2.
Literature 1H chemical shifts assigned to low pH form of serine protease active site imidazolium Cɛ1—H protons and pKa values
| Sample | δ, ppm | pKa | Ref. |
|---|---|---|---|
| Inactive or degraded forms | |||
| α-Lytic protease | 8.0 | 5.6 | Westler & Markley§ |
| α-Chymotrypsin | 8.54 | 6.18 | Markley & Ibanez (20) |
| α-Lytic protease | 8.70 | 6.5 | Markley (21) |
| α-Lytic protease, “fresh” | 8.65 | 6.5 | Markley et al. (22) |
| α-Lytic protease, “aged” | 8.71 | 5.9 | Markley et al. (22) |
| α-Lytic protease | 8.65 | 6.5 | Westler et al. (23) |
| Subtilisin Carlsberg | 8.6 | 7.22 | Jordan et al. (24) |
| Subtilisin BPN′ | 8.61 | 7.23 | Bycroft & Fersht (25) |
| Questionable | |||
| Porcine trypsin | 8.32 | 4.5 (slow) 5.0 (fast) | Markley & Porubcan (26) |
| Not in question | |||
| Chymotrypsinogen | 9.21 | 7.33 | Markley & Ibanez (20) |
| Porcine trypsinogen | 9.12 | 7.67 | Porubcan et al. (39) |
| Bovine trypsinogen | 9.12 | 7.72 | Porubcan et al. (39) |
| α-Lytic protease + DIFP | 8.38 | 8.16 | Extracted from Porubcan et al. (40) |
| Subtilisin E + AAPbF | 9.20 | NA | Bao et al. (41) |
| α-Chymotrypsin + AAPbF | 9.24 | NA | Bao et al. (41) |
| α-Chymotrypsin + TFMK | 8.97–9.18 | 10.7–12.1 | Lin et al. (42) |
| α-Chymotrypsin | 9.20 | — | Bao et al. (43) |