Table 2.
Apparent kinetic parameters determined for wild-type and mutant CNS. Apparent kinetic parameters, kcat, Km(CTP) and Km(Neu5Ac) were obtained by fitting initial rates of reactions measured at varying concentrations of one substrate, at a fixed concentration of the other, to the Michaelis–Menten equation using nonlinear regression. The fixed concentrations were [CTP] = 0.154 mm and [Neu5Ac] = 0.615 mm.
| kcat(app) (min−1) CTP | Km(app) (μm) CTP | kcat(app)/Km(app) (μm−1·min−1) CTP | kcat(app) (min−1) Neu5Ac | Km(app) (μm) Neu5Ac | kcat(app)/Km(app) (μm−1·min−1) Neu5Ac | |
|---|---|---|---|---|---|---|
| WT | 540 ± 30 | 34 ± 5 | 16 | 540 ± 10 | 130 ± 9 | 4.1 |
| Q104A | – | – | – | 110 ± 9 | 4700 ± 900 | 0.024 |
| Q104L | 0.17 ± 0.01 | 150 ± 20 | 1.1 × 10−3 | – | – | 2.9 × 10−4 ± 1 × 10−5 |
| Q104E | 0.046 ± 0.001 | 200 ± 9 | 2.3 × 10−4 | 0.027 ± 0.001 | 310 ± 40 | 8.7 × 10−5 |
| Q104N | 0.74 ± 0.03 | 32 ± 4 | 0.023 | – | – | 7.5 × 10−4 ± 2 × 10−5 |
| K142A | 0.056 ± 0.002 | 140 ± 10 | 3.8 × 10−4 | – | – | 3.6 × 10−5 ± 2 × 10−6 |