N-Oxygenation of chlorpromazine by human FMO3 and FMO1
The oxygenation of chlorpromazine was determined by monitoring the appearance of N-oxide associated with the N-oxygenation of chlorpromazine as described under Materials and Methods. Data are mean ± standard deviation.
Enzyme | n | Km | Vmax | Vmax/Km |
|---|---|---|---|---|
| μM | nmol/min/mg protein | ml/min/mg protein | ||
| FMO3 MBP | 9 | 60.6 ± 59.5 | 32.0 ± 20.7 | 0.7 ± 0.3 (100)a |
| Ala360-FMO3 MBP | 9 | 80.2 ± 30.5 | 42.6 ± 7.9 | 0.6 ± 0.1 (86) |
| His360-FMO3 MBP | 12 | 27.6 ± 5.4 | 6.5 ± 5.4 | 0.2 ± 0.1** (29) |
| Gln360-FMO3 MBP | 3 | 76.2 ± 3.6 | 48.5 ± 1.0 | 0.6 ± 0.0 (86) |
| Pro360-FMO3 MBP | 9 | 26.0 ± 20.8 | 27.4 ± 18.3 | 1.2 ± 0.2 (171) |
| FMO1 MBP | 3 | 58.4 ± 3.2 | 175.0 ± 13.0 | 3.0 ± 0.1 (100)b |
| Pro360-FMO1 MBP | 6 | 22.4 ± 3.0† | 86.2 ± 12.6† | 3.8 ± 0.5† (126) |
↵** p < 0.01 vs. values for wild-type FMO3 enzyme, according to Kruskal-Wallis statistical analysis, which was run to compare values for FMO3 variants.
↵† p < 0.05 vs. value for wild-type FMO1 enzyme, according to the Mann-Whitney test, which was run to compare values for FMO1 variant with wild-type enzyme.
↵ a The values in parentheses represent the percentage of Vmax/Km compared with the corresponding value for wild-type FMO3.
↵ b The values in parentheses represent the percentage of Vmax/Km compared with the corresponding value for wild-type FMO1.