Table 1. Comparison of binding of p-substituted phenols by the different GST–SYE proteins.
The SYE proteins were titrated with the indicated phenolic ligands for which the phenolic pKa of the free ligand (according to [39]) is given. The dissociation constants (μM) Kd±S.D. derived from the titration data are given, and the absorbance maximum of each of the long-wavelength CT complexes, CTmax (nm), is shown in parentheses. *, no detection of long-wavelength optical transitions.
| Ligand | pKa | SYE1 | GST–SYE1 | SYE3 | GST–SYE3 | SYE4 | GST–SYE4 |
|---|---|---|---|---|---|---|---|
| Pentafluorophenol | 5.40 | 19.23±4.23 (550) | * | 32.11±12.22 (560) | * | 1.99±0.26 (550) | 0.95±0.21 (560) |
| p-Nitrophenol | 7.05 | 2.38±0.47 (550) | 73.59±28.70 (550) | 9.71±3.75 (555) | 76.76±16.55 (550) | 2.09±0.17 (550) | 5.14±1.41 (550) |
| p-Hydroxybenzaldehyde | 7.62 | 4.90±1.04 (570) | 29.96±6.85 (560) | 11.64±3.45 (570) | 28.01±7.66 (570) | 4.20±0.34 (555) | 2.30±0.49 (550) |
| p-Cyanophenol | 7.90 | 4.43±0.62 (570) | 26.21±5.68 (578) | 3.61±1.13 (560) | 44.96±18.46 (580) | 6.72±0.96 (550) | 10.11±2.62 (560) |
| p-Hydroxyacetophenone | 8.05 | 4.00±0.10 (571) | 35.84±8.73 (574) | 7.10±2.59 (575) | 28.20±6.51 (580) | 3.51±0.81 (570) | 8.10±1.92 (580) |
| p-Chlorophenol | 9.34 | * | * | * | * | 17.25±3.53 (604) | 44.98±14.00 (622) |
| p-Fluorophenol | 9.43 | * | * | * | * | 51.15±24.57 (629) | 14.35±1.71 (620) |
| p-Methoxyphenol | 10.20 | * | * | * | * | 94.26±56.83 (650) | 92.19±28.94 (686) |
| p-Cresol | 10.30 | * | * | * | * | 29.47±12.98 (642) | 68.46±14.10 (645) |