TABLE 6.
Isotope effects data obtained for the E78Q, E122Q, and E78Q/E122Q
All isotope effects were measured in the direction of saccharopine formation. Lysine was varied while maintaining NADH and α-Kg at saturation (>10 Km) at 25 °C. Data were measured at the following pH values: 7.2 for E78Q and E122Q and 7 for E78Q/E122Q. Wild type data are included for comparative purposes.
| Parameter | Wild type SDH | E78Q | E122Q | E78Q/E122Q |
|---|---|---|---|---|
| D(V) | 1.50 ± 0.07 | 1.48 ± 0.04 | 1.60 ± 0.01 | 1.30 ± 0.03 |
| D(V/KLys) | 1.60 ± 0.05 | 1.48 ± 0.04 | 2.30 ± 0.04 | 1.30 ± 0.03 |
| D2O(V) | 2.2 ± 0.1 | 2.5 ± 0.1 | 1.96 ± 0.04 | 2.01 ± 0.06 |
| D2O(V/KLys) | 1.9 ± 0.1 | 2.5 ± 0.1 | 1.96 ± 0.04 | 2.01 ± 0.06 |
| D2O(V)D | 1.76 ± 0.08 (80% D2O) | 2.40 ± 0.04 | 1.60 ± 0.01 | 1.200 ± 0.001 |
| D2O(V/KLys)D | 1.86 ± 0.08 (80% D2O) | 1.60 ± 0.03 | 1.60 ± 0.01 | 1.400 ± 0.003 |