TABLE 2.
Decarboxylation of pyruvate and branched-chain 2-oxo acids by cell extracts of wild-type S. cerevisiae and isogenic strains affected in the expression of one or more PDC genes
| Strain (genotype) | 2-Oxo acid decarboxylation by cell extracts (U/mg of protein)b
|
|||
|---|---|---|---|---|
| Pyruvate | α-Keto-isovalerate | α-Keto-β-methyl valerate | α-Keto isocaproate | |
| T2-3Da (wild type) | 0.70 ± 0.05 | 0.082 (12%) | 0.027 (4%) | 0.039 (6%) |
| GG 570a (Δpdc1 Δpdc5 Δpdc6) | <0.003 | <0.003 | <0.003 | <0.003 |
| T2-3Dc (wild type) | 1.08 ± 0.03 | 0.129 (12%) | 0.070 (7%) | 0.064 (6%) |
| GG 567c (PDC1 Δpdc5 Δpdc6) | 0.81 ± 0.03 | 0.122 (15%) | 0.046 (6%) | 0.051 (6%) |
| GG 569c (Δpdc1 PDC5 Δpdc6) | 0.36 ± 0.02 | 0.064 (18%) | 0.026 (7%) | 0.029 (8%) |
a
Cells from carbon-limited chemostat cultures.
b
Data are the averages of at least two independent assays; standard deviations were less than 20% for all assays. Percentages in parentheses indicate the activity with branched-chain substrates relative to the rate of pyruvate decarboxylation.
c
Cells from exponential-phase shake flask cultures (see Materials and Methods).