Table 5.
Specific decarboxylase activities for aromatic, branched-chain, and sulfur-containing 2-oxo acids in cell extracts of S. cerevisiae strains expressing individual genes with sequence similarity to genes encoding TPP-dependent decarboxylasesa
| Strain (gene regulation)b | Phenylpyruvate |
Ketoisovalerate |
Ketoisocaproate |
Ketomethylvalerate |
4-Methylthio-2-oxo-butanoate |
|||||
|---|---|---|---|---|---|---|---|---|---|---|
| Mean Vmax (μmol · mg of protein−1 · min−1) ± SD | Mean Km (mM) ± SD | Mean Vmax (μmol · mg of protein−1 · min−1) ± SD | Mean Km (mM) ± SD | Mean Vmax (μmol · mg of protein−1 · min−1) ± SD | Mean Km (mM) ± SD | Mean Vmax (μmol · mg of protein−1 · min−1) ± SD | Mean Km (mM) ± SD | Mean Vmax (μmol · mg of protein−1 · min−1) ± SD | Mean Km (mM) ± SD | |
| IMZ030 (PDC1 ↑) | BD | NA | 38 ± 5 | >20 | 15 ± 3 | >20 | 9 ± 4 | >20 | 41 ± 9 | >20 |
| IMZ024 (PDC5 ↑) | 68 ± 9 | 0.67 ± 0.07 | 46 ± 16 | >20 | 19 ± 4 | >20 | 8 ± 1 | >20 | 54 ± 2 | >20 |
| IMZ031 (PDC6 ↑) | BD | NAa | 31 ± 5 | >20 | 19 ± 3 | >20 | 10 ± 1 | >20 | 51 ± 7 | >20 |
| IMZ002 (ARO10 ↑) | 201 ± 29 | 0.14 ± 0.01 | 103 ± 33 | 12 ± 2 | 103 ± 11 | 2.1 ± 0.2 | 103 ± 10 | 4.7 ± 0.5 | 85 ± 4 | 5.36 ± 0.7 |
| IMZ025 (THI3 ↑) | BD | NA | BD | NA | BD | NA | BD | NA | BD | NA |
| IMZ001 (Pdc−) | BD | BD | BD | BD | BD | BD | BD | BD | BD | BD |
a
Shown are data and mean results from single-component Michaelis-Menten fits of the averages of technical replicates (n = 2) of results from two independent chemostat cultures. NA, not applicable; BD, below the detection limit with a Vmax of <8 nmol · mg of protein−1 · min−1.
b
↑ denotes overexpression of the TPP-dependent 2-oxo acid decarboxylase.