NAT1 4 and NAT1 14B kinetic constants determined in vitro (per milligram of total protein)
PABA, ABP, and N-OH-ABP constants were determined at a fixed concentration of 100 μM CoASAc. Table values represent mean ± S.E.M. for three to six individual determinations. Differences were tested for significance by Student's t test.
| Allele | Substrate | km(app) | Vmax(app) | Vmax/km(app) | kcat(app) | kcat/km(app) |
|---|---|---|---|---|---|---|
| μM | nmoles · min−1 · mg−1 | ml · min−1 · mg−1 | min−1 | min−1/μM | ||
| NAT1*4 | PABA | 42.9 ± 3.3 | 116 ± 3 | 2.72 ± 0.21 | 2400 ± 57 | 56.5 ± 4.3 |
| NAT1*14B | 430 ± 1a | 18.5 ± 1.5b | 0.043 ± 0.002b | 1550 ± 97b | 3.61 ± 0.20b | |
| NAT1*4 | ABP | 273 ± 46 | 57.7 ± 5.8 | 0.218 ± 0.018 | 1200 ± 122 | 4.52 ± 0.38 |
| NAT1*14B | 65.6 ± 3.9b | 18.0 ± 4.3b | 0.280 ± 0.031 | 1760 ± 128 | 22.9 ± 0.23c | |
| NAT1*4 | N-OH-ABP | 141 ± 1.1 | 2.97 ± 0.19 | 0.0211 ± 0.0014 | 35.1 ± 68 | 0.250 ± 0.02 |
| NAT1*14B | 46.8 ± 1.3b | 1.76 ± 0.03b | 0.038 ± 0.001c | 147 ± 7a | 3.15 ± 0.23c |