Table 1.
Kinetic parameters for the hydrolysis of p-NP-Neu5Ac by the pneumococcal sialidases computed using the direct and the indirect spectrophotometric assays (see Materials and Methods for details)
| |
p-
NP-Neu5Ac direct method |
p-NP-Neu5Ac indirect method |
||||
|---|---|---|---|---|---|---|
| k cat (s -1 ) | K m (μM) | k cat / K m (M - 1·s -1 ) | k cat (s -1 ) | K m (μM) | k cat / K m (M - 1·s -1 ) | |
| NanA* |
>175 |
>500 |
(3.5 ± 0.3) × 105 |
>490 |
>1,100 |
(8.4 ± 0.9) × 104 |
| NanB* |
>0.14 |
>500 |
(2.7 ± 0.3) × 102 |
>11 |
>1,200 |
(1.1 ± 0.1) × 102 |
| NanC* | >17 | >500 | (3.4 ± 0.3) × 104 | >11 | >700 | (1.2 ± 0.1) × 104 |
* first order reaction kinetics were observed with this substrate at concentrations up to 500 μM (direct method) or 1,200 μM (indirect method) and thus only allowed to compute the kcat/K m values.