Table I.
Specific activities of the human SULT1A1, SULT1A3, SULT1B1 and SULT1C4 with ractopamine and salbutamol as substratesa.
| Specific activity (nmol/min/mg) |
||||
|---|---|---|---|---|
| Substrate | SULT1A1 | SULT1A3 | SULT1B1 | SULT1C4 |
| Ractopamine | ||||
| 1 µM | NDb | 5.41 ± 0.05 | ND | ND |
| 10 µM | 0.37 ± 0.06 | 41.36 ± 0.37 | ND | 0.60 ± 0.02 |
| 50 µM | 1.36 ± 0.03 | 91.86 ± 3.50 | 0.26 ± 0.03 | 3.61 ± 0.12 |
| Salbutamol | ||||
| 1 µM | ND | 0.27 ± 0.01 | ND | ND |
| 10 µM | ND | 2.01 ± 0.03 | ND | ND |
| 50 µM | ND | 9.93 ± 0.53 | ND | ND |
aSpecific activity refers to nmol substrate sulfated/min/mg purified enzyme. Data represent mean ± standard deviation derived from three determinations. The concentrations of the substrate used in the assay mixtures were 1, 10, or 50 µM.
bND refers to activity not detected. Specific activity determined was lower than the detection limit (estimated to be ∼0.01 nmol/min/mg protein).