Table 2.
Kinetic parameters for the neomorphic reaction, conversion of αKG to D2HG, catalyzed by IDH1
Values result from fits of kinetic data using two different enzyme preparations. The standard error is determined from the deviance from these hyperbolic fits (Fig. 4, supplemental Fig. S4).
| IDH1 | Relative hydrophobicity of residue 132a | van der Waals volume of side chain at residue 132, Å3b | kcat (37 °C) | Km,αKG (37 °C) | Km,NADPH (37 °C) | Efficiency (kcat/Km,αKG, 37 °C) | kcat, s−1 (21 °C) | Km,αKG (21 °C) | Km,NADPH (21 °C) | Efficiency (kcat/Km,αKG, 21 °C) |
|---|---|---|---|---|---|---|---|---|---|---|
| s−1 | mm | mm−1 s−1 | s−1 | mm | mm−1 s−1 | |||||
| WT | −14 (Arg) | 148 (Arg) | 0.019 ± 0.001 | 0.5 ± 0.3 | ≤ 0.010 | 0.04 ± 0.02 | ≤ 0.017 | NDc | ND | ND |
| H133Q | −14 (Arg) | 148 (Arg) | ≤ 0.016 | ND | ND | ND | ≤ 0.034 | ND | ND | ND |
| A134D | −14 (Arg) | 148 (Arg) | ≤ 0.019 | ND | ND | ND | ≤ 0.020 | ND | ND | ND |
| R100Q | −14 (Arg) | 148 (Arg) | 0.34 ± 0.02 | 12 ± 2 | 0.005 ± 0.003 | 0.028 ± 0.005 | 0.128 ± 0.006 | 10 ± 1 | ≤ 0.0025 | 0.013 ± 0.001 |
| R132H | 8 (His) | 118 (His) | 4.2 ± 0.3 | 1.1 ± 0.3 | ≤ 0.025 | 3.8 ± 0.9 | 0.43 ± 0.04 | 1.8 ± 0.6 | ≤ 0.005 | 0.24 ± 0.08 |
| R132C | 49 (Cys) | 86 (Cys) | 1.60 ± 0.07 | 0.36 ± 0.05 | 0.010 ± 0.009 | 4.4 ± 0.6 | 0.84 ± 0.03 | 0.36 ± 0.06 | ≤ 0.025 | 2.3 ± 0.4 |
| R132G | 0 (Gly) | 48 (Gly) | 1.59 ± 0.09 | 0.34 ± 0.08 | <0.025 | 5 ± 1 | 0.45 ± 0.02 | 0.30 ± 0.05 | ≤ 0.025 | 1.5 ± 0.2 |