TABLE 1.
NADH- and NADPH-dependent enzymatic reductions of various α-keto acids by the MJ1425-encoded enzyme, the MJ0490-encoded enzyme, and the MF-malate dehydrogenase
| Substrate | Cosubstratea | MJ1425 (MdhI)
|
MJ0490 (MdhII)
|
MF (MdhIII)
|
||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Km (mM) | Vmax (U/mg) | Vmax/Km (min−1 mg−1) | Km (mM) | Vmax (U/mg) | Vmax/Km (min−1 mg−1) | Km (mM) | Vmax (U/mg) | Vmax/Km (min−1 mg−1) | ||
| Oxalacetate | NADH | 0.13 ± 0.01 | 47 ± 2.0 | 356 | 0.25 ± 0.03 | 29 ± 1.9 | 120 | 0.11 ± 0.027 | 27 ± 1.6 | 240 |
| Oxalacetate | NADPH | 5.32 ± 1.0 | 38 ± 3.6 | 7 | 0.30 ± 0.03 | 49 ± 1.5 | 160 | 0.95 ± 0.20 | 34 ± 2.8 | 36 |
| Sulfopyruvate | NADH | 0.04 ± 0.008 | 370 ± 22 | 10,000 | 1.3 ± 0.032 | 43 ± 4.1 | 34 | 0.07 ± 0.019 | 120 ± 14 | 1,700 |
| Sulfopyruvate | NADPH | 0.21 ± 0.026 | 31 ± 1.7 | 148 | 0.19 ± 0.019 | 69 ± 5.0 | 590 | 0.21 ± 0.017 | 81 ± 2.3 | 390 |
| α-Ketoglutarate | NADH | 1.9 ± 0.3 | 49 ± 3.2 | 26 | NAb | NA | ||||
| KHTCA | NADH | 15 ± 6.7 | 6 ± 2.1 | 0.4 | NA | NA | ||||
a
The cosubstrate concentrations were 0.3 mM NADH and 0.3 mM NADPH.
b
NA, no activity detectable (<0.1 U/mg) at substrate concentrations up to 10 mM.