TABLE 6.
Steady-state kinetic parametersa for Draeh and Npueh1 acting on each enantiomer of pNSO (substrate 5) and pNPGE (substrate 10)
| Enzyme and parameter | Value for indicated enantiomer
|
|||
|---|---|---|---|---|
| (R)-pNSO | (S)-pNSO | (R)-pNPGE | (S)-pNPGE | |
| Draeh | ||||
| kcat (s−1) | >0.007 | >0.17 | >0.7 | >0.5 |
| Km (mM) | >0.5 | >0.5 | >0.3 | >0.3 |
| kcat/Km (mM−1 s−1) | 0.020 | 0.42 | 2.8 | 2.1 |
| E valueb | 21 (21) | 21 (21) | 1.3 (1.8) | 1.3 (1.8) |
| Npueh1 | ||||
| kcat (s−1) | >0.2 | 3.4 | >2.6 | 0.42 |
| Km (mM) | >0.5 | 0.20 | >0.025c | 0.028 |
| kcat/Km (mM−1 s−1) | 0.60 | 17 | 174 | 15 |
| E valueb | 28 (17) | 28 (17) | 12 (15) | 12 (15) |
a
Since for some enzymes the Km value exceeded substrate solubility, only lower limits could be determined for kcat and Km, and kcat/Km values were determined as first-order rate constants.
b
Calculated from the kcat/Km ratios of the two enantiomers. The E value calculated from a kinetic resolution experiment is given in parentheses.
c
At higher substrate concentrations, substrate inhibition occurred; therefore, kcat/Km could be determined only as a first-order rate constant at a low substrate concentration.