Table 2.
Enzyme activity with model substrates and lactose
| Substrate | Enzyme | kcat (min-1) | KM (mM) | kcat/KM (mM-1min-1) |
|---|---|---|---|---|
| pNPGlc | wt-BglX | 1.02 ± 0.12 | 0.95 ± 0.08 | 1.07 ± 0.04 |
| pNPGlc | D287G | NA | NA | NA |
| pNPGlc | E293Q | 0.46 ± 0.05 | 3.2 ± 0.3 | 0.14 ± 0.03 |
| pNPGlc | D111N | NA | NA | NA |
| oNPGlc | wt-BglX | 1.08 ± 0.12 | 12.0 ± 1.0 | 0.090 ± 0.003 |
| oNPGlc | D287G | NA | NA | NA |
| oNPGlc | E293Q | 0.47 ± 0.05 | 6.7 ± 1.8 | 0.070 ± 0.012 |
| oNPGlc | D111N | NA | NA | NA |
| oNPGal | wt-BglX | 282 ± 30 | 0.21 ± 0.02 | 1343 ± 15 |
| oNPGal | D287G | 22.8 ± 2.4 | 0.14 ± 0.02 | 163 ± 6 |
| oNPGal | E293Q | 54.0 ± 0.6 | 0.21 ± 0.02 | 257± 21 |
| oNPGal | D111N | 46.2 ± 4.8 | 0.51 ± 0.02 | 91 ± 6 |
| Lactose | wt-BglX | 2.64 ± 0.24 | 6.8 ± 1.0 | 0.39 ± 0.02 |
| Lactose | D287G | NA | NA | NA |
| Lactose | E293Q | 0.33 ± 0.05 | 6.7 ± 1.0 | 0.049 ± 0.001 |
| Lactose | D111N | NA | NA | NA |
NA: no activity.