Table 5.
Effects of iodothyronamines on the phenolic ring deiodination of rT3 by Dio1 from mouse liver membrane fractions
| Substrate of Dio1 | Apparent Km(μm) | Apparent Vmax (pmol/mg·min) | Ki (μm) | Mode of inhibition | |
|---|---|---|---|---|---|
| Vehicle | NA | 0.43 ± 0.02 | 142.7 ± 2.7 | NA | NA |
| 3′,5′-T2AM (5 μm) | Phenolic ring | 1.19 ± 0.1a | 136.4 ± 4.8a | 2.6 ± 0.4 | Mixed |
| 3,3′-T2AM (5 μm) | Phenolic ring | 0.86 ± 0.04a | 136.9 ± 2.9a | 4.8 ± 1.1 | Mixed |
| rT3AM (5 μm) | Phenolic ring | 0.42 ± 0.01 | 31.3 ± 2.3a | 1.3 ± 0.2 | Noncompetitive |
| T3AM (5 μm) | Tyrosyl ring | 0.43 ± 0.03 | 124.5 ± 4.7a | 34.0 ± 2.6 | Noncompetitive |
| 3,5-T2AM (5 μm) | Tyrosyl ring | 0.42 ± 0.02 | 134.9 ± 2.1a | 85.0 ± 7.7 | Noncompetitive |
| T4AM (5 μm) | No Dio1 substrate | 0.43 ± 0.03 | 144.2 ± 4.1 | NA | NA |
| 3′-T1AM (5 μm) | No Dio1 substrate | 0.42 ± 0.04 | 141.9 ± 1.4 | NA | NA |
| 3-T1AM (5 μm) | No Dio1 substrate | 0.43 ± 0.03 | 142.1 ± 5.2 | NA | NA |
The apparent Km, Vmax, and Kivalues are from three separate experiments performed in triplicate and are presented as mean ± sd. NA, Not applicable.
a
Statistical difference with P < 0.05 as determined by Friedman test followed by Dunn’s post test.