TABLE 3.
Activities of enzymes involved in the EMP pathway and the pathway leading to the biosynthesis of sugar nucleotides and EPS in cell extracts of the EPS-producing strain S. thermophilus LY03a
| Enzyme | Avg activity (nmol · mg of cell protein−1 · min−1) ± SD at indicated time point with:
|
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.22 M lactose
|
0.15 M lactose + 0.14 M fructose
|
0.15 M lactose + 0.14 M galactose
|
0.15 M lactose + 0.14 M glucose
|
|||||||||
| 1 | 2 | 3 | 1 | 2 | 3 | 1 | 2 | 3 | 1 | 2 | 3 | |
| α-Phosphoglucomutase | 581 ± 44 | 829 ± 7 | 715 ± 18 | 567 ± 72 | 717 ± 11 | 673 ± 30 | 429 ± 9 | 603 ± 7 | 523 ± 20 | 590 ± 42 | 897 ± 58 | 831 ± 6 |
| β-Phosphoglucomutase | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 |
| UDP-glucose pyrophosphorylase | 137 ± 11 | 199 ± 2 | 175 ± 5 | 147 ± 21 | 171 ± 3 | 161 ± 8 | 108 ± 2 | 155 ± 8 | 142 ± 11 | 148 ± 11 | 224 ± 14 | 208 ± 2 |
| UDP-galactose 4-epimerase | 281 ± 60 | 396 ± 38 | 351 ± 44 | 252 ± 39 | 297 ± 6 | 277 ± 14 | 183 ± 4 | 275 ± 15 | 258 ± 16 | 277 ± 18 | 410 ± 25 | 382 ± 3 |
| dTDP-glucose pyrophosphorylase | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 2 ± 1 | 1 ± 0 | 1 ± 1 | 3 ± 1 | 1 ± 0 |
| Dehydratase | 15 ± 1 | 20 ± 1 | 14 ± 2 | 8 ± 1 | 12 ± 1 | 8 ± 2 | 30 ± 2 | 36 ± 3 | 25 ± 1 | 18 ± 3 | 31 ± 1 | 17 ± 1 |
| Epimerase reductase | 0 ± 0 | 2 ± 1 | 1 ± 1 | 0 ± 0 | 2 ± 1 | 0 ± 0 | 0 ± 0 | 2 ± 0 | 0 ± 1 | 0 ± 0 | 2 ± 0 | 0 ± 0 |
| Phosphoglucose isomerase | 1,635 ± 253 | 2,034 ± 327 | 1,984 ± 76 | 2,167 ± 225 | 2,167 ± 294 | 2,061 ± 321 | 1,371 ± 197 | 1,496 ± 53 | 1,467 ± 50 | 2,084 ± 26 | 2,523 ± 103 | 2,112 ± 256 |
| 6-Phosphofructokinase | 1,832 ± 100 | 2,478 ± 148 | 2,444 ± 270 | 2,239 ± 230 | 2,425 ± 90 | 2,306 ± 154 | 1,778 ± 161 | 1,830 ± 65 | 1,795 ± 61 | 2,132 ± 27 | 2,582 ± 106 | 2,161 ± 262 |
| Fructose 1,6-bisphosphatase | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 3 ± 3 | 20 ± 3 | 1 ± 1 |
a
S. thermophilus LY03 was grown in batch cultures in MRS broth on lactose and combinations of lactose and glucose, lactose and galactose, and lactose and fructose as carbohydrate sources at 42°C and a constant pH of 6.2. Samples were taken at three time points of the fermentation course, representing the exponential growth phase (point 1), the end of the exponential growth phase (point 2), and the stationary phase (point 3). Each value is the average of at least three measurements.