Enzyme | Dopamine | 4-Nitrophenol | ||||
---|---|---|---|---|---|---|
Km | Vmax | Vmax/Km | Km | Vmax | Vmax/Km | |
μm | nmol/min/mg | μm | nmol/min/mg | |||
Wild-type SULT1A3 | 2.2 | 501 | 228 | 1382 | 426 | 0.31 |
SULT1A3 H143Y | 5.6 | 455 | 81 | 1469 | 252 | 0.17 |
SULT1A3 E146A | 127 | 187 | 1.5 | 6.1 | 104 | 17 |
SULT1A3 H143Y/E146A | 87 | 211 | 2.4 | 9.4 | 148 | 16 |
Wild-type SULT1A1 | 109 | 37 | 0.34 | 3.8 | 405 | 107 |
Data shown are the average of duplicate determinations performed using PAPS at a concentration of 13 μm. Enzyme activities of wild-type SULT1A3 and SULT1A3 H143Y were measured with dopamine concentrations between 0.13 and 26.7 μm, whereas for SULT1A3 E146A and H143Y/E146A mutants and wild-type SULT1A1, the concentration range used was 0.013–1.3 mm. Enzyme activities of wild-type SULT1A3 and SULT1A3 H143Y were measured with 4-nitrophenol concentrations between 0.013 and 1.3 mm, whereas for SULT1A3 E146A and H143Y/E146A mutants and wild-type SULT1A1, the concentration range used was 0.13–26.7 μm.