Table 1.
Thermodynamic parameters of NADH and NAD+ binding with the αβ, αγ and α2βγ enzymes of human NAD-IDH analyzed by ITC at 20 °C.
| Protein | K d (μ M) a | ΔH (kcal/mol) | TΔS | n-value |
|---|---|---|---|---|
| For NADH | ||||
| αβ (30 μM/0.8 mM)b | 4.6 ± 0.7 | −16.6 ± 0.7 | −9.03 | 1.26 ± 0.04 |
| αγ (100 μM/4 mM) | 109.0 ± 19.5 | −8.1 ± 1.3 | −2.62 | 2.19 ± 0.27 |
| α2βγ (30 μM/2 mM) | 46.3 ± 6.5 | −21.8 ± 2.7 | −14.8 | 2.53 ± 0.25 |
| For NAD+ | ||||
| αβ (200 μM/4 mM) | 268.1 ± 28.4 | −5.0 ± 0.7 | −0.2 | 1.14 ± 0.11 |
| αγ (100 μM/4 mM) | ND | ND | ND | ND |
| α2βγ (100 μM/8 mM) | WB | WB | WB | WB |
aAbbreviations: Kd, dissociation constant; ND, not detectable; WB, weak binding.
bNumbers in parentheses refer to the concentrations of titrand (protein)/titrant (NADH or NAD+) in the measurements.