Table 1.
Kinetic analysis of S. Typhimurium transketolases
| Reaction substratesa | Vmax | Km | kcat | kcat/Km |
|---|---|---|---|---|
| μm NADH consumed/s | μm | s−1 | m−1 s−1 | |
| Transketolase A | ||||
| Excess X5P | ||||
| R5P | 992 ± 60 | 730 ± 110 | 9.54 × 104 | 1.31 × 108 |
| E4P | 1079 ± 97 | 99 ± 20 | 1.04 × 105 | 1.05 × 109 |
| Excess R5P | ||||
| X5P | 1362 ± 42 | 270 ± 30 | 1.31 × 105 | 4.77 × 108 |
| Excess E4P | ||||
| X5P | 743 ± 36 | 170 ± 30 | 7.14 × 104 | 4.22 × 108 |
| Transketolase B | ||||
| Excess X5P | ||||
| R5P | 690 ± 25 | 660 ± 60 | 6.71 × 104 | 1.02 × 108 |
| E4P | 888 ± 57 | 82 ± 10 | 8.65 × 104 | 1.06 × 109 |
| Excess R5P | ||||
| X5P | 806 ± 25 | 290 ± 30 | 7.85 × 104 | 2.69 × 108 |
| Excess E4P | ||||
| X5P | 539 ± 33 | 180 ± 40 | 5.25 × 104 | 2.99 × 108 |
| Transketolase C* | ||||
| Excess X5P | ||||
| R5P | 15.5 ± 1.1 | 58 ± 14 | 1.35 × 103 | 2.32 × 107 |
| E4P | 16.0 ± 0.7 | 23 ± 4 | 1.39 × 103 | 6.07 × 107 |
| Excess R5P | ||||
| X5P | 9.4 ± 0.5 | 75 ± 18 | 8.16 × 102 | 1.08 × 107 |
| Excess E4P | ||||
| X5P | 7.8 ± 0.3 | 120 ± 15 | 6.71 × 102 | 5.58 × 106 |
a Kinetics of each purified enzyme were analyzed for each of the canonical transketolase reactions. Each substrate was assessed while the co-substrate was present in excess. Values for Vmax and Km represent mean and S.D. X5P, xylulose 5-phosphate; R5P, ribose 5-phosphate; E4P, erythrose 4-phosphate.