Table 4.
Apparent Km and Vmax of selected TAM deiodination reactions as measured by LC-MS/MS
| Deiodinase isozyme | Deiodinase preparation | Substrate | Km (μm substrate) | Vmax (pmol deiodinated product/mg protein·min) |
|---|---|---|---|---|
| Dio1 | HepG2 | rT3AM | 0.63 ± 0.05 | 1.5 ± 0.08 |
| Dio2 | MSTO-211H | rT3AM | 0.006 ± 0.002 | 0.088 ± 0.012 |
| Dio3 | ECC-1 | T3AM | 0.017 ± 0.004 | 1.9 ± 0.2 |
| Dio3 | ECC-1 | 3-T1AM | 1.2 ± 0.05 | 2.4 ± 0.06 |
The apparent Km and Vmax values were determined by LC-MS/MS-based deiodinase assays using an incubation time of 30 min and 10 nm to 5 μm of the indicated thyronamine as substrate. The values represent the mean ± sd from three separate experiments performed in triplicate.