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

SubstrateCosubstrateaMJ1425 (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)
OxalacetateNADH0.13 ± 0.0147 ± 2.03560.25 ± 0.0329 ± 1.91200.11 ± 0.02727 ± 1.6240
OxalacetateNADPH5.32 ± 1.038 ± 3.670.30 ± 0.0349 ± 1.51600.95 ± 0.2034 ± 2.836
SulfopyruvateNADH0.04 ± 0.008370 ± 2210,0001.3 ± 0.03243 ± 4.1340.07 ± 0.019120 ± 141,700
SulfopyruvateNADPH0.21 ± 0.02631 ± 1.71480.19 ± 0.01969 ± 5.05900.21 ± 0.01781 ± 2.3390
α-KetoglutarateNADH1.9 ± 0.349 ± 3.226 NAb NA
KHTCANADH15 ± 6.76 ± 2.10.4NANA
  • 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.