Table VI.
Regulatory properties of the mutant LK417MSwt
| Kinetic Constant | Reaction
|
|
|---|---|---|
| Pyrophosphorolysis | Synthesis | |
| Specific activity | 45 units mg−1 | 12 units mg−1 |
| 3-PGA activation | 14-fold | >100-fold |
| A0.5 3-PGA (−Pi) | 7 μm | 450 μm |
| A0.5 Ratio mutant/wt | 3.5 | 4.5 |
| A0.5 3-PGA (+0.5 mm Pi) | 198 μm | — |
| A0.5 Ratio +Pi/−Pi | 28 | — |
| I0.5 Pi | 20 μm | — |
The mutant LK417MSwt was expressed, purified, and the kinetic parameters determined as described in Methods. The substrates and cofactors were 2 mm ADP-Glc, 1.5 mm PPi, and 7 mm Mg2+ in the pyrophosphorolysis direction, and 1.5 mm ATP, 0.5 mm Glc-1-P, and 7 mm Mg2+ in the synthesis direction. The results are the average of two independent experiments and the difference between them was less than 10% in all cases.