TABLE 2.
Specific activities of glycolytic enzymes in cell extracts of aerobic glucose-limited chemostat cultures (D, 0.10 h−1) of various S. cerevisiae strainsa
| Enzyme | Sp act (U · mg of protein−1) in:
|
||
|---|---|---|---|
| CEN.PK113-7D (wild type) | GG293 (empty vector) | GG393 (Pdc overproducer) | |
| Hexokinase (EC 2.7.1.1) | 1.7 ± 0.1 | 1.8 ± 0.1 | 1.6 ± 0.2 |
| Phosphoglucose isomerase (EC 5.3.1.9) | 2.8 ± 0.2 | 2.9 ± 0.2 | 2.4 ± 0.1 |
| Phosphofructokinase (EC 2.7.1.11) | 0.3 ± 0.04 | 0.4 ± 0.04 | 0.3 ± 0.04 |
| Fructose-1,6-diphosphate aldolase (EC 4.1.2.13) | 1.0 ± 0.02 | 1.0 ± 0.1 | 0.8 ± 0.03 |
| Triosephosphate isomerase (EC 5.3.1.1) | 52.5 ± 4.1 | 57.7 ± 1.4 | 45.3 ± 2.3 |
| Glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12) | 5.6 ± 0.3 | 5.3 ± 0.2 | 4.4 ± 0.1 |
| Phosphoglycerate kinase (EC 2.7.2.3) | 7.4 ± 0.1 | 6.5 ± 0.2 | 6.7 ± 0.4 |
| Phosphoglycerate mutase (EC 2.7.5.3) | 6.8 ± 0.4 | 6.5 ± 0.3 | 5.9 ± 0.4 |
| Enolase (EC 4.2.1.11) | 0.7 ± 0.02 | 0.7 ± 0.01 | 0.6 ± 0.03 |
| Pyruvate kinase (EC 2.7.1.40) | 2.9 ± 0.1 | 2.6 ± 0.1 | 2.4 ± 0.2 |
| Pdc (EC 4.1.1.1) | 0.6 ± 0.1 | 0.6 ± 0.03 | 8.4 ± 0.5 |
| Alcohol dehydrogenase (EC 1.1.1.1) | 9.1 ± 0.4 | 9.6 ± 0.5 | 6.1 ± 0.1 |
a
Data are presented as the average ± standard deviation for duplicate enzyme assays on two independent cultures. Glycolytic flux for hexose and triose intermediates was estimated from the specific ethanol production rate in an off-line fermentation assay. Calculations of the flux were based on a soluble protein content of 33% (33). For strains CEN.PK113-7D, GG293, and GG393, glycolytic flux values for hexose and triose intermediates were 0.37, 0.38, and 0.39 U · mg of protein−1 and 0.75, 0.76, and 0.78 U · mg of protein−1, respectively.