TABLE 3.
ITC of the binding of CBM60s to carbohydrate ligands
ITC was carried out in 50 mm Na Hepes buffer, pH 7.5, containing 5 mm CaCl2 at 25 °C.
| Ligand |
CjCBM60A |
||||
|---|---|---|---|---|---|
| Ka × 105 | ΔG | ΔH | TΔS | na | |
| m−1 | kcal mol−1 | kcal mol−1 | kcal mol−1 | ||
| Soluble oat-spelt xylan | 4.0 ± 0.4 | −7.6 | −13.1 ± 0.2 | −5.5 | 0.92 ± 0.01 |
| Birchwood xylan | 7.3 ± 0.5 | −8.0 | −11.5 ± 0.09 | −3.5 | 0.88 ± 0.01 |
| Wheat arabinoxylan | 9.8 ± 8.6 | −8.2 | −9.1 ± 0.08 | −0.9 | 0.92 ± 0.01 |
| Rye arabinoxylan | 1.3 ± 0.07 | −7.0 | −8.2 ± 0.1 | −1.2 | 1.1 ± 0.01 |
| Methylglucuronoxylan | 7.5 ± 0.7 | −8.0 | −10.3 ± 0.1 | −2.3 | 0.98 ± 0.01 |
| Hydroxyethylcellulose | 0.13 ± 0.01 | −5.6 | −2.3 ± 0.2 | 3.3 | 1.05 ± 0.06 |
| Barley β-glucan | 4.2 ± 0.7 | −7.7 | −5.6 ± 0.2 | 2.1 | 0.95 ± 0.02 |
| Lichenan | 1.8 ± 0.2 | −7.2 | −4.1 ± 0.1 | 3.1 | 1.06 ± 0.02 |
| Xyloglucan | 12.3 ± 2.0 | −8.3 | −2.6 ± 0.0 | 5.7 | 1.01 ± 0.02 |
| Lupin galactan | 7.2 ± 1.1 | −8.0 | −12.4 ± 0.2 | −4.4 | 1.01 ± 0.01 |
| Lupin pectic galactan | 3.3 ± 0.5 | −7.5 | −7.7 ± 0.2 | −0.2 | 1.01 ± 0.02 |
| Potato galactan | 2.2 ± 0.2 | −7.3 | −7.7 ± 0.2 | −0.4 | 0.96 ± 0.01 |
| Potato pectic galactan | 1.1 ± 0.1 | −6.9 | −9.3 ± 0.3 | −2.4 | 1.04 ± 0.02 |
| Ligand |
vCBM60 |
||||
|---|---|---|---|---|---|
| Ka × 103 | ΔG | ΔH | TΔS | na | |
| m−1 | kcal mol−1 | kcal mol−1 | kcal mol−1 | ||
| Soluble oat-spelt xylan | 7.2 ± 0.8b | −5.3 | −6.6 ± 1.0 | −1.2 | 1.09 ± 0.15 |
| Birchwood xylan | 5.9 ± 0.1 | −5.2 | −7.8 ± 0.4 | −2.6 | 1.01 ± 0.05 |
| Wheat arabinoxylan | 4.3 ± 0.1 | −5.0 | −9.1 ± 0.1 | −4.1 | 1.05 ± 0.0 |
| Rye arabinoxylan | 3.8 ± 0.2 | −4.9 | −8.4 ± 0.9 | −3.5 | 1.10 ± 0.11 |
| Hydroxyethylcellulose | 6.2 ± 0.9 | −5.2 | −8.4 ± 1.4 | −3.2 | 1.04 ± 0.18 |
| Barley β-glucan | 8.7 ± 0.9 | −5.4 | −8.4 ± 1.0 | −3.0 | 1.01 ± 0.11 |
| Lichenan | 5.5 ± 0.4 | −5.1 | −7.6 ± 0.9 | −2.5 | 1.05 ± 0.11 |
| Xyloglucan | 4.3 ± 0.6 | −5.0 | −10.4 ± 0.4 | −5.4 | 1.02 ± 0.32 |
| Lupin galactan | 8.1 ± 0.4 | −5.3 | −9.9 ± 0.8 | −4.6 | 1.05 ± 0.07 |
| Potato galactan | 10.2 ± 0.6 | −5.5 | −10.1 ± 0.6 | −4.6 | 1.00 ± 0.05 |
| Lupin pectic galactan | 4.5 ± 0.3 | −5.0 | −12.2 ± 1.4 | −7.2 | 1.00 ± 0.15 |
| Potato pectic galactan | 12.2 ± 0.6 | −5.6 | −10.3 ± 0.4 | −4.7 | 1.01 ± 0.03 |
| Rhamnogalacturonan | n.b.c | − | − | − | |
| Arabinan sugar beet | n.b. | − | − | − | |
| Xylohexaose | 9.8 ± 1.2 | −5.4 | −7.1 ± 0.9 | −1.7 | 1.01 ± 0.11 |
| Xylopentaose | 10.1 ± 0.8 | −5.5 | −6.6 ± 0.3 | −1.1 | 1.05 ± 0.07 |
| Xylotetraose | 13.9 ± 1.2 | −5.7 | −5.7 ± 0.3 | 0.0 | 1.00 ± 0.06 |
| Xylotriose | 9.3 ± 0.7 | −5.4 | −5.6 ± 0.3 | −0.2 | 0.96 ± 0.07 |
| Cellohexaose | 3.2 ± 0.4 | −4.8 | −8.2 ± 2.9 | −3.4 | 1.00 ± 0.32 |
| Cellopentaose | 5.3 ± 0.1 | −5.1 | −5.3 ± 0.1 | −0.2 | 0.99 ± 0.18 |
| Cellotetraose | 3.4 ± 0.2 | −4.8 | −5.3 ± 0.4 | −0.5 | 1.05 ± 0.13 |
| Cellotriose | 4.1 ± 0.5 | −4.9 | −6.1 ± 0.12 | −1.2 | 1.03 ± 0.36 |
| Galactotriose | 16.5 ± 1.1 | −5.6 | −10.5 ± 0.5 | −4.9 | 1.00 ± 0.04 |
| Galactobiose | 13.4 ± 1.3 | −5.6 | −8.3 ± 0.7 | −2.7 | 1.01 ± 0.07 |
| Mannohexaose | n.b. | ||||
a The ITC data were fitted to a single site binding model for all ligands. For polysaccharide ligands in which the molar concentration of binding sites is unknown, the n-value was iteratively fitted to as close as possible to one, by adjusting the molar concentration of the ligand (see Ref. 11).
b The errors are presented, for the experimentally determined values for typical titrations.
c n.b., no binding.