TABLE 1.
Binding parameters and inhibition of 14DM activity by posaconazole, fluconazole, and VNF
| TC14DM | No azole | Posaconazole | Fluconazole | VNF |
|---|---|---|---|---|
| Azole binding: spectral titrations of ferric form | ||||
| Soret band maximum (nm) | 418.5 | 422.5 | 422.5 | 424.5 |
| Apparent Kd (μm) | 0.06 ± 0.01 (1.9 ± 0.12)a | 0.44 ± 0.03 (40 ± 2.11) | 0.07 ± 0.01 (0.3 ± 0.04) | |
| Influence on CO complex formation: ferrous form | ||||
| Rate (%/min) | 80 | ndd | 22 | ndd |
| Total (%) | 100 | <5 | 70 | <5 |
| Inhibitory effect on 14DM catalysis | ||||
| I/E2b | <1 (40) | 1.8 (>200) | <1 (>200) | |
| Activity at 1:1 molar ratio I/E (%)c | ||||
| Initial rate | 0 | 70 | 0 | |
| Substrate conversion after a 1-h reaction | 0 | 100 | 0 | |
a Data in parentheses are for the human 14DM ortholog.
b This refers to the molar ratio inhibitor/enzyme that causes a 2-fold decrease in the initial rate of catalysis (12).
c The P450 concentration in the reaction was 1 μm (see “Experimental Procedures”).
d nd, not determined.