Table 5.
Km and Vmax values for l-arabinose and d-glucose for Gal2 variants with amino acid substitutions at positions N376 and T89. Transport kinetics were measured by uptake studies with radioactive sugars after expression of GAL2 alleles in S. cerevisiae DS68625. Values are average and mean deviation of two independent sets of uptake experiments. The detection limit for d-glucose uptake (Vmax) was 1.8 nmol−1 (mg biomass)−1 min−1. Data used to calculate Km and Vmax values are shown in Additional File 13.
| Km (mM) | Km ratio | Vmax (nmol (mg biomass)−1 min−1) | |||
|---|---|---|---|---|---|
| Gal2 variant | l-arabinose | d-glucose | Ara/Glc | l-arabinose | d-glucose |
| Gal21 | 335 ± 21 | 1.9 ± 0.2 | 176 | 75 ± 5 | 26 ± 1 |
| Gal2N376I | 117 ± 16 | 101 ± 47 | 1 | 39 ± 3 | 32 ± 18 |
| Gal2N376S | 186 ± 33 | 38 ± 1 | 5 | 64 ± 2 | 28 ± 1 |
| Gal2N376T | 171 ± 17 | 57 ± 1 | 3 | 65 ± 2 | 17 ± 4 |
| Gal2T89I + N376T | 103 ± 40 | - | - | 30 ± 2 | <1.8 |
| Gal2T89I | 99 ± 18 | 7 ± 0.2 | 15 | 22 ± 3 | 13 ± 0.1 |
1kinetic data for wild-type Gal2 were derived from Bracher et al. (2018).