Table 2.
Comparative kinetic analysis of the AROM protein with the wild-type and mutant isolated AROM dehydroquinate synthase domains
| Enzyme | Substrate | Km μM | Specific activity U mg−1 | Turnover number |
| Wild-type and mutant DHQS | ||||
| Wild-type DHQS | DAHP | 21 (2) | 9.50 | 6.8 |
| NAD+ | 1.9 (0.1) | |||
| R130K mutant DHQS | DAHP | 228 (19) | 0.07 | |
| NAD+ | 14.1 (1.5) | |||
| R130A mutant DHQS | NA | — | — | |
| K152A mutant DHQS | NA | — | — | |
| H275L mutant DHQS | NA | — | — | |
| R264A mutant DHQS | NA | — | — | |
| Pentafunctional AROM | ||||
| DHQS domain | DAHP | 9.3 (0.9) | 1.78 | 5.1 (19.0) |
| NAD+ | 0.7 (0.04) | |||
| Type 1 dehydroquinase domain | DHQ | 40 (3) | 3.63 | 10.5 (19.4) |
| Shikimate dehydrogenase domain | DHS | 311 (18) | 0.52 | 1.5 (51.2) |
| NADPH | 13.5 (1.5) | |||
| Shikimate kinase domain | ATP | 4800 (342) | 5.35 | 15.4 (18.3) |
| Shikimate | 22.3 (1.2) | |||
NA = not applicable.
The Km and the turnover number for the native AROM protein, the wild-type DHQS domain and the mutant R130K DHQS domain are shown. All values were calculated using GRAFIT, standard errors for each Km measurement are given in brackets. The values given in brackets following the turnover number are the published values for the equivalent AROM protein of N. crassa (Lambert et al. 1985; Coggins et al. 1987a).